September 29, 1888.] 



THE GAIWENERS' CHRONICLE. 



351 



net, and a strong wire for the same purpose runs 

 along the wall at a height of \2 feet. Next the 

 ground wire netting is used to prevent the 

 ordinary net from rotting. 



Mr. Da vies strongly recommends the treatment 

 of Poinsettias advocated in the Gardeners' 

 Chronicle four years ago by Mr. Denning. He 

 has planted out the same plants in the kitchen 

 garden three years in succession. After having 

 been cut down they are allowed to " break ; " 

 the balls are then reduced, and they are planted 

 outdoors early in June, and taken indoors again 

 the first week in September, when they are 

 treated in the usual way. It is found that ten 

 weeks of " Nature " strengthens the plants im- 

 mensely. They become bushy, and produce 

 several bracts. Solanums and Bouvardias are 

 treated in the same manner, the former going 

 outdoors in May when shabby, and coming in 

 again, full of berries at the end of September. 

 Bouvardias are turned out the first week in June, 

 and taken in at the end of August, to flower two 

 months afterwards. 



The glory of the kitchen garden for ornament 

 and perf ume is a double row of Lavender, planted 

 five years since, one row on each side of a central 

 path 600 feet in length, running through the 

 garden. At the end of August the Lavender was 

 in full blossom. Chiswick Favourite Potato 

 produced last year five sieves per rod, and is 

 yielding a large crop this year, free from disease. 

 Veitch's Main Crop Onion is well formed, has 

 good bulbs even in this year of too much top, 

 keeps well, and is considered by Mr. Davies to be 

 the best Onion in cultivation. I have seen beds 

 this year all leaf, many bulbs of Main Crop weigh 

 here § lb. each. H. E. 



PLANT -LIFE. 



{Concluded from p. 323.) 



Referring to the assigned causes of variation, 

 Mr. Dyer continued : — 



" Though it is difficult to establish the fact that 

 external causes promote variation directly, it is 

 worth considering whether they may not do so indi- 

 rectly. Weissmann, like Lamarck before him, has 

 pointed out, as others have also done, the remarkable 

 persistence of the plants and animals of Egypt ; and 

 the evidence of this is now even stronger. We owe, 

 at Kew, to the kindness of Dr. Schweinfurth, a col- 

 lection of specimens of plants from Egyptian tombs 

 which are said to be as much as 4000 years old. 

 They are still perfectly identifiable, and, as one cf 

 my predecessors in this chair has pointed out, they 

 differ in no respect from their living representatives 

 in Egypt at this day. The explanation which 

 Lamarck gave of this fact ' may well,' says Sir 

 Charles Lyell, ' lay claim to our admiration.' He 

 attributed it, in effect, to the persistence of the phi - 

 Bical geography, temperature, and other natural coi - 

 ditions. The explanation seems to me adequate. 

 The plants and animals, we may fairly assume, were, 

 4000 years ago. as accurately adjusted to the condi- 

 tions in which they then existed as the fact of their 

 persistence in the country shows that they must be 

 now. Any deviation from the type that existed then 

 would either, therefore, be disadvantageous or indif- 

 ferent. In the former case it would be speedily 

 eliminated, in the latter it would be swamped by 

 cross-breeding. But we know that if seeds of these 

 plants were introduced into our gardens we should 

 soon detect varieties amongst their progeny. Long 

 observation upon plants under cultivation has always 

 disposed me to think that a change of external con- 

 ditions actually stimulated variation, and so gave 

 natural selection wider play and a better chance of 

 re-establishing the adaptation of the organism to 

 them. Weissmann explains the remarkable fact 

 that organisms may for thousands of years reproduce 

 themselves unchanged by the principle of the per- 

 sistence of the germ-plasm. Yet it seems hard to 

 believe that the germ-plasm, while enshrined in the 

 individual whose race it is to perpetuate, and nou- 

 rished at its expense, can be wholly indifferent to all 

 its fortunes. It may be so, but in that case it would be 

 very unlike other living elements of organised beings. 



Variation' in" Cultivated Plaxts.^ 

 " I am bound, however, to confess that I am not 

 wholly satisfied with the data for the discussion of 

 this question which practical horticulture supplies. 

 That the contents of our gardens do exhibit the 

 results of variation in a most astonishing degiee no 

 one will dispute. But for scientific purposes any 

 exact account of the treatment under which these 

 variations have occurred is unfortunately usually 

 wanting. A great deal of the most striking varia- 

 tion is undoubtedly due to wide crossing, and these 

 cases must, of course, be eliminated when the object 

 is to test the independent variation of the germ- 

 plasm. Hoffman, whose experiments I have already 

 referred to, doubts whether plants do as a matter of 

 fact vary more under cultivation than in their native 

 home and under natural conditions. It would be 

 very interesting if this could be tested by the con- 

 certed efforts of two cultivators, say, for example, in 

 Egypt and in England. Let some annual plant be 

 selected, native of the former country, and let its 

 seed be transmitted to the latter. Then let each 

 cultivator select any variations that arise in regard 

 to some given character ; set to work, in fact, ex- 

 actly as any gardener would who wanted to ' improve ' 

 the plant, but on a preconcerted plan. A com- 

 parison of the success which each obtained would be 

 a measure of the effect of the change of the environ- 

 ment on variability. If it proved that, as Hoffman 

 supposed, the change of conditions did not affect 

 what we may call the rate of variation, then, as Mr. 

 Darwin remarks in writing to Professor Semper, 

 ' the astonishing variations of almost all cultivated 

 plants must be due to selection and breeding from 

 the varying individuals. This idea,' he continues, 

 ' crossed my mind many years ago, but I was afraid 

 to publish it, as I thought that people would say, 

 How he does exaggerate the importance of selection.' 

 From an independent consideration of the subject I 

 also find my mind somewhat shaken about it. Yet 

 I feel disposed to say with Mr. Darwin, ' I still must 

 believe that changed conditions give the impulse to 

 variability, but that they act in most cases in a very 

 indirect manner.' 



" Whatever conclusions we arrive at on these 

 points, every one will agree that one result of the 

 Darwinian theory has been to give a great impulse 

 to the study of organisms, if I may say so, as ' going 

 concerns.' Interesting as are the problems which 

 the structure, the functions, the affinity, or the geo- 

 graphical distribution of a plant may afford, the 

 living plant in itself is even more interesting still. 



Adaptation of fobm to purpose. 

 " Every organ will bear interrogation to trace the 

 meaning and origin of its form, and the part it plays 

 in the plant's economy. That there is here an im- 

 mense field for investigation there can be no doubt. 

 Mr. Darwin himself set us the example in a series of 

 masterly investigations. But the field is well-nigh 

 inexhaustible. The extraordinary variety of form 

 which plants exhibit has led to the notion that 

 much of it may have arisen from indifferent varia- 

 tion. No doubt, as Mr. Darwin has pointed out, 

 when one of a group of structures held together by 

 some morphological or physiological nexus varies, the 

 rest will vary correlativelv. One variation then 

 mav, if advantageous, become adaptive, while the 

 rest will be indifferent. But it appears to me that 

 such a principle should be applied with the greatest 

 caution, and from what I have myself heard fall 

 from Mr. Darwin, I am led to believe that in the 

 later years of his life he was disposed to think that 

 every detail of plant structure had some adaptive 

 significance, if only the clue could be found to it. 

 As regards the forms of flowers an enormous body of 

 information has been collected, but the vegetative 

 organs have not yet yielded their secret to anything 

 like the same extent. My own impression is that 

 they will be found to be adaptive in innumerable 

 ways which at present are not even suspected. At 

 Kew we have probably a larger number of species 

 assembled together than are to be found anywhere 

 on the earth's surface. Here, then, is ample material 

 for observation and comparison. But the adaptive 

 significance will doubtless often be found by no 

 means to lie on the surface. Who, for example, 

 could possibly have guessed by inspection the pur- 

 pose of the glandular bodies on the leaves of Acacia 

 sphaerocephala, and on the pnlvinus of Cecropia 

 peltata, which Belt in the one case, and Fritz Miiller 

 in the other, have shown to serve as food for ants ? 

 So far from this explanation being far-fetched, Belt 

 found that the former ' tree is actually unable to 

 exist without its guard,' which it could not secure 

 without some attraction in the shape of food. One 



fact which strongly impresses me with a belief in the 

 adaptive significance of vegetative characters is the 

 fact that they are constantly adopted in almost 

 identical forms by plants of widely different affinity. 

 If such forms were without significance one would 

 expect them to be infinitely varied. If, however, 

 they are really adaptive, it is intelligible that differ- 

 ent plants should independently avail themselves of 

 identical appliances and expedients. 



Botanical Laboratories. 



" Although this country is splendidly equipped with 

 appliances for the study of systematic botany, our 

 universities and colleges fall tar behind a standard 

 which would be considered even tolerable on the Con- 

 tinent in the means of studying morphological and 

 physiological botany, or of making researches in these 

 subjects. There is not at the moment anywhere in 

 London an adequate botanical laboratory, and though 

 at most of the universities matters are not quite so bad, 

 still I am not aware of any one where it is possible to 

 do more than give the routine instruction or to allow 

 the students, when they have passed through this, to 

 work for themselves. It is not easy to see why this 

 should be, because on the animal side the accomoda- 

 tion and appliances for teaching comparative anatomy 

 and physiology are always adequate and often palatial. 

 Still less explicable to me is the tendency on the part 

 of those who have charge of medical education to 

 eliminate botanical study from the medical curriculum, 

 since historically the animal histologists owe every- 

 thing to botanists. 



" In the seventeenth century, as I have already 

 mentioned, Hooke first brought the microscope to 

 the investigation of organic structure, and the tissue 

 he examined was cork. Somewhat later, Grew, in 

 his Anatomy of Plants, gave the first germ of the cell 

 theory. During the eighteenth century the anato- 

 mists were not merely on a hopelessly wrong tack 

 themselves, but they were bent on dragging botanists 

 into it also. It was not till 1837, a little more than 

 fifty years ago, that Henle saw that the structure of 

 epithelium was practically the same as that of the 

 parenchyma plantarum, which Grew had described 

 150 years before. Two years later Schwann pub- 

 lished his immortal theory, which comprised the 

 ultimate facts of plant and animal anatomy under 

 one view. But it was to a botanist, Von Mohl, that, 

 in 1846, the biological world owed the first clear 

 description of protoplasm, and to another botanist, 

 Cohn (1851), the identification of this with the 

 sarcode of zoologists. 



" I do not myself believe that any better access 

 can be obtained to the structure and functions of 

 living tissues than by the study of plants. How- 

 ever, I am not without hopes that the serious 

 botany in the laboratory will be in time better cared 

 for. I do not hesitate to claim for it a position 

 of the greatest importance in ordinary scientific 

 education. All the essential phenomena of living 

 organisms can be readily demonstrated upon plants. 

 The necessary appliances are not so costly, and the 

 work of the class-room is free from many difficulties 

 with which the student of the animal side of biology 

 has to 'contend. The splendid laboratory on Ply- 

 mouth Sound, the erection of which we owe to the 

 energy and enthusiasm of Professor Ray Lankester, 

 is open to botanists as well as to zoologists. At Kew 

 we owe to private munificence a commodious labora- 

 tory in which much excellent work has already been 

 done. And this Association has made a small grant 

 in aid of the establishment of a laboratory in the 

 Royal Botanic Garden at Peradeniya in Ceylon. It 

 may be hoped that this will afford facilities for work 

 of the same kind as has yielded Dr. Treub such a rich 

 harvest of results in the Buitenzorg Botanic Garden.' 



Nectarines and Evolution.— In Downing's 



Fruits and Fruit Trees of America he says, " The 

 Nectarine is known in Northern India, where it is 

 called moondla aroo (smooth Peach). It appears to 

 be only a distinct accidental variety of the Peach, 

 and this is rendered quite certain, since there are 

 several well-known examples on record of both 

 Peaches and Nectarines having been produced on 

 the same branch, thus showing a disposition to 

 return to the natural form. Nectarines, however, 

 usually produce Nectarines again on sowing the 

 seeds ; but they also occasionally produce Peaches. 

 The Boston Nectarine originated from a Peach- 

 stone." Is this a proof of an individual creation, or 

 does it favour evolution ? Are there any other cases 

 of a similar nature [plenty. Ed., G.C.]. See Londc n 

 Gardeners' Magazine, i.. p. 471 ; xiv.. p. 53. W. M. B , 

 Pittsburg Pa, 'in " English Mechanic" 



