THE FARMER'S MAGAZINE. 



conditions, variations which not only affect their structure, 

 but declare themselves in a difference in constitution. Some of 

 these differences of constitution are transmissible, as also 

 the differences in the details of the minor parts of their 

 organization. The preservation of peculiarities of this 

 kind, transmitted through generations, results in the 

 formation of what are called races of plants. When 

 we see a variation of species, a particular modification, 

 falling within the specific type, which presents desirable 

 qualities in regard to structure or constitution, we endeavour 

 to preserve it, and cultivation is, to a great extent, devoted to 

 the preservation, the continuance, and improvement of races 

 established in this way. It is because the constitution of these 

 variations of the original form is favourable that we endeavour 

 to preserve them ; and when we have firmly fixed these pecu- 

 liarities in a series of forms, generation after generation, we 

 have produced a " race." The varieties on which these races 

 are fouuded may perhaps be attributable, in the first iustance, 

 to physical conditions ; these conditions may have produced 

 the orit^inal modification from which the race takes its character. 

 By this I would not admit, tor a moment, that the external 

 conditions may transform one species, properly so called, into 

 another; but every species has a certain range of differences, 

 and external conditions may c;ill out one or other of these 

 inodifications uuder particular circumstances. I think it pro- 

 bable that most variations of particular species may have been 

 produced by external conditions in the first instance; it is true 

 also that the external conditions have great influence in pre- 

 serving these characters in races ; but we find that in old- 

 established races the character is preserved with a certain 

 obstinacy iu spite of e.xternal conditions, and that the running 

 back or reverting of such races is alow. The races which are 

 cultivated chit fly iu this country — races of Wheat, plants be- 

 longing to the Cabbage tribe, Turnips, Cauliflower, and so on 

 — are most of them very old, and we have little information 

 as regards their origin. Gardeners prosecute this part of cul- 

 tivation — the formation of races — very actively; and with 

 florists especially the production and establishment of races is 

 one of the most important departments of their art, being as 

 important to them as the importation and introduction of new 

 species. They obtain these different races by sowing large 

 quantities of seed, selecting the specimens which come up of 

 the form which they require, saving these alone, and repeating 

 the process generation after generation, getting rid of all the 

 forms which are most like the original parent. It has been ob- 

 served by cultivators that there are certain peculiarities in the 

 product of these successive sowings, which can scarcely be 

 called unexpected, because we see the same thing illustrated 

 in the races of animals and even in the human race. Two 

 general rulps are derived by gardeners from the observation 

 of the phenomena presented in this production of races by 

 successive sowings. The first is that like produces like. 

 They save the seed only of the variation which they wish 

 to preserve, and the probability is that it will prcduce its like. 

 This, however, is by no meaus certain, as every one knows. 

 The seed of any variety produces a great number of varieties 

 of which only a part are like tbe immediate parent. It is 

 found that there is a tendency for several generations to run 

 back to some of the former generations, in contradistinction to 

 the rule that like produces like, and this is called by physiolo- 

 gists atavisM, or a " takmg after " their ancestors. M. Vilmo. 

 rin, a distinguished Belgian florist, thinks that the best way of 

 breaking this tendency to run back to the ancestral type— to 

 take after 11 eir grandfathers or c.rcatgrandfatlicrs, instead of 

 their fathers— is to select for a number of generations those 

 forms which are least like the origiml parent ; to get the forms 



as far as possible away from the original type, in the first in- 

 stance, before proceeding to select the absolute form which is 

 required. After a certain number of generations, however, of 

 course, this atavism will begin to act on the same side as the 

 tendency of like to produce like. If we get a number of 

 generations of the race resembling one another generation after 

 generation, of course the tendency to go back to the ancestors 

 will not tend to alter the plant, because it will have a long line 

 of similar ancestors before it, where it will not find the 

 differences which it did in the original case. From this it 

 follows that the older a race is, the more it is fixed. If a par- 

 ticular form has a long line of similar ancestors, the tendency 

 to run back to the form of its ancestors co-operates with the 

 tendency to be like its immediate parent; both these work to 

 the same end, and the practical deduction is that races recently 

 established have little or no fixity ; that the older a race is, the 

 more firmly and surely its peculiarities are fixed. We have 

 illustrations of this iu the human race, and amongst the most 

 striking may be mentioned the Jewish race, undo\ibtedly one 

 of the most ancient, iu which we see fixity so strikingly marked 

 under such very different external conditions. In this second 

 part of ray discourse I have directed attention to the importance 

 of physiology iu reference to races. The subject of races is 

 one which belongs particularly to physiology as distinguished 

 from organic chemistry ; as also does the constitution of species 

 or kinds of plants, of which I have previously spoken. 



The third head of my lecture has reference to the con- 

 stitution of particular organs. No organ, perhaps, is of 

 more interest in this respect, or presents a greater variety 

 of conditions, having relation to practice, than the root. 

 It is very much the case with those who take merely a 

 chemical view of phj'siology, to regard the root as a kind 

 of absorbing machine, as a process of prolongation of the 

 structure into the soil (serving like the lower part of the 

 wick of a lamp) to absorb the nourishment contained in the 

 roil. Such a view as this is a very partial view of the 

 nature of the root, and leaves out of consideration the 

 most important of its physiological characters. In the first 

 place, roots are very d liferent in their kinds. We have 

 two classes of roots among the flowering plants, examples 

 of which occur among commonly cultivated plants. We 

 have roots such as are produced bj' the turnip, by the bean, 

 and various leguminous plants ; and we have roots produced 

 by the dilTerent kinds of grass and grain plants, where 

 there is an original difference in the structure, a ditference 

 depending on the modes in which they first sprout from 

 their seed. One class produces a large root; the class to 

 which the turnip and bean belong produces a main tnmk, 

 a continuation of the lower part of the stem, from which 

 the different absorbing branches are given off as the 

 branches are from the trunk above. In the grass and corn 

 plants there is never any main trunk of that kind produced, 

 but a variable number of fibres or filaments thrown out 

 from the bottom of the stem, as we see from the bottom of 

 a Hyacinth bulb when growing in a glass. The number of 

 these and their vigour depend greatly upon the stimulus 

 applied to the plant at the base of the stem when the roots 

 are sprouting. The number is not fixed in any given plant ; 

 it varies to a great extent in proportion to the supply of food 

 furnished to the plant. 



But when developed in either of these ways, plants do not 

 all send their roots at once into the soil to absorb the food in 

 the seme way. We have ordinary plants growing down into 

 the soil ; theu we have a large class growing in water ; and in 

 addition to these there are others which never make their way 

 into tbe earth or into the water, but are supplied by the 



