yaii. 6, 18S7] 



NA TURE 



THE FORMS OF SEEDLINGS : THE CAUSES 



TO WHICH THEY ARE DUE^ 

 CIR JOHN LUBBOCK commenced the lectuie with some 

 '-' general remarks on the innumerable types of foUage among 

 mature plants and the causes to which we might refer their 

 various forms, the breadth of some and narrowness of others, 

 the differences of position, the difl'erences of length in conifers, 

 &c. He said that these considerations had led him to study the 

 cotyledon- or first leaves of seedlings. Cotyledons do not pre- 

 -ent such extreme differences as leaves ; nevertheless, they 

 iflford a very wide range. Some are broad, some narrow, some 

 are long, some short, some are stalked, some sessile, somelobed, 

 some even bifid or trifid. At first sight these differences seem 

 interminable, and it might appear hopeless to attempt to ex- 

 plain them. Sir John Lubbock, however, pointed out, as re- 

 gards many species, taking especially the commonest plants, 

 such as the familiar mustard and cress, the beech, sycamore, 

 pink, chickweed, &c., the conditions of their formation and 

 growth, and it is beautiful to see the various reasons to which 

 the differences are due, gradually unfolding themselves ; the 

 same result being sometimes brought about by very different 

 circumstances — emargination of the cotyledons, for instance, 

 being due to at least six different causes. He mentioned one 

 curious peculianiy in the seedling of a species allied to our 

 common mistletoe. It is a parasitic species, and its fruit, like 

 that of the mistletoe, is somewhat viscid, so that it adheres to 

 any plant on which it falls. But, even if it reaches the plant on 

 which it grows, it may light on an unsuitable position — say, for 

 instance, a leaf. What then happens ? The radicle elongates 

 for about an inch, and then develops on its tip a flattened di~k, 

 which applies itself to the plant. If the situation be suitable, 

 there it grows ; if not, the radicle straightens itself, tears the 

 beri-y from the spot where it is lying, curves itself, and then 

 brings the berry doivn on to a new spot. The radicle then de- 

 taches itself, curves in its turn, and thus finds a new point of 

 attachment. We are assured that this has been seen to happen 

 several times in succession, and that the young plant thus seems 

 enabled to select a suitable situation. 



The form of the cotyledons, or seed-leaves, depends greatly 

 on that of the seeds, long narrow seeds naturally, in most in- 

 stances, producing embiyos with narrow cotyledons. The cases, 

 however, which can be so simply accounted for are compara- 

 tively few. Many plants with narrow cotyledons have flattened 

 and orbicular seeds. In such species, however, the cotyledons 

 lie transversely to the seed. An interesting case is afforded by 

 the pink family, where the pink itself has broad cotyledons, 

 while the chickweed has narrow ones. In both cases the seeds 

 are flattened and orbicular, but in the pink the seed is dorsally 

 compressed, and the cotyledons lie in the broad axis of the seed; 

 while in the chickweed the seed is laterally flattened, and the 

 cotyledons lie transversely to the seed. 



Another veiy interesting case which he gave is that of the 

 genus Galium, to which the common " cleavers" of our hedges 

 belongs. Here also we find some species with narrow, some 

 with broad, cotyledons ; but the contrast seems to be due to a 

 very dift'erent cause. Galium aparinc has broad, Galium sac- 

 chavatum narrow, cotyledons. So far as the form of the seed 

 is concerned, there is no reason why the cotyledons should not 

 be much broader than they are. The explanation may perhaps 

 be found in the structure of the pericarp, which is thick, tough, 

 and corky. It is very impervious to water, and may be advan- 

 tageous to the embryo by resisting the attacks of drought and of 

 insects, and perhaps even, if the seed be swallowed by a bird, 

 Vjy protecting it from being dige.-ted. It does not split open, 

 and is too tough to be torn by the embryo. The cotyledons, 

 therefore, if they h.ad widened as they might otherwise have 

 done, would have found it impossible to emerge from the seed. 

 They evade the difficulty, however, by remaining narrow. On 

 the other hand, in Galittm aparinc the pericarp is much thinner, 

 and the embryo is able to tear it open. In this case, therefore, 

 the cotyledons can safely widen without endangering their exit 

 from the seed. The thick corky covering of Galium sacchar- 

 alum is, doubtless, much more impervious to water than the 

 comparatively thin test of Galium aparine. The latter species 

 is a native of our own isles, while Galium saciharalum inhabits 

 Algiers, the hotter parts of France, &c. May not then, perhaps, 

 he suggested, the thick corky envelope be adapted to enable it 



' Lecture at the Royal Institution, May 21 

 Bart., M.P., D.C.L., LL.D., F.K.S., M.k.L 



, by Sir John Lubbock, 



to withstand the heat and drought. In this genus, as in many 

 other plants, the embryo occupies only a part of the seed, being 

 surrounded by a store of food or " perisperm." In many cases 

 the embryo occupies the whole seed, and the cotyledons must, 

 therefore, in large seeds, either be thrown into various folds, as 

 in the beech, or be thick and fleshy, as in the bean or oak. The 

 rea:ons for their numerous differences open up an inexhaustible 

 variety of interesting questions. Sir John gave a great number 

 of examples, which were rendered clearer by mean^ of numerous 

 diagrams of seeds and seedlings. 



In conclusion, he said it might be asked whether the embryo 

 conformed to the seed, or the seed to the embryo, and showed 

 that, at least as regards certain species, the former was the case ; 

 while the shape of the seed, again, might be shown to be in- 

 fluenced by considerations connected with the construction of 

 the fruit. In reply to this he compared the seedlings of the 

 sycamore and of the oak. In the sycamore, the seed is more or 

 less an oblate spheroid, and the cotyledons, which are long and 

 ribbon-like, being rolled up into a ball, fit it closely, the inner 

 cotyledon being generally somewhat shorter than the others. 

 On the other hand, the nuts of the beech are triangular. An 

 arrangement like th.it of the sycamor-; would therefore be utterly 

 un uitable, as it would necessarily leave great gaps. The 

 cotyledons, however, are folded up somewhat like a fan, but 

 with more complication, and in such a manner that they fit 

 beautifully into the triangular nut. Can we, hosvever, he said, 

 carry the argument one stage further ? Why should the seed of 

 the sycamore be globular, and that of the beech triangular? Is 

 it clear that the cotyledons are constituted so as to suit the 

 seed? May it not be that it is the seed which is adapted to the 

 cotyledons ? In answer to this, we must exatiine the fruit, and 

 we shall find that in both cases the cavity of the fruit is approxi- 

 mately spherical. That of the sycamore, however, is compara- 

 tively small, and contains one seed, which more or less exactly 

 conforms to the cavity in which it lies. In the beech, on the 

 contrary, the fruit is at least twice the diameter, and contains 

 from two to four nuts, which consequently, in order to occupy the 

 space, are compelled (to give a familiar illustration, like the pips of 

 an orange) to take a more or less triangular form. Thus then, he 

 said in conclusion, in these cases, starting with the form of the 

 fruit, we see that it governs that of the seed, and that the seed 

 again determines that of the cotyledons. But, though the 

 cotyledons often follow the form of the seed, this is not inva- 

 riably the case. Other circumstances, as I have attempted to 

 show, must also be taken into consideration, and we can throw 

 much light on the varied forms which seedlings assume. 



I fear you may consider that I have occupied your time by a 

 multiplicity of details, and I wish I could hope to have made 

 those little plants half as interesting to you as they have made 

 themselves to me ; but, at any rate, I may plead that without 

 minute, careful, and loving study, we cannot hope in science to 

 arrive at a safe and satisfactory generalisation. 



The lecture was accompanied not only by numerous diagrams, 

 but by specimens, kindly lent by the authorities of Kew, and by 

 some practical illustrations. 



ON THE USE AND EQUIPMENT OF 

 ENGINEERING LABORA TORIES 



A T the ordinary meeting of the Institution of Civil Engineers, 

 -^ on Tuesday, December 21, 1S86, Mr. Edward Woods, 

 President, in the chair, the paper read was on "The Use and 

 Equipment of Engineering Laboratories," by Prof. Alex. B. W. 

 Kennedy, M.Inst.C.E. The author believed that it was 

 essential for a young engineer to obtain his practical training, in 

 the ordinary sense of the expression, in a workshop. But the 

 practical training of a workshop was incomplete even on its own 

 ground, and there appeared to be plenty of room for practical 

 teaching such as might fairly fall within the scope of a scientific 

 institution, and which should at the same time supplement and 

 complete workshop experience without overlapping it. In an 

 ordinary pupilage a young engineer did not have much oppor- 

 tunity of studying such things as the physical properties of the 

 iron and steel with which he had to deal, nor the strength 

 of tho e materials, nor the efficiency of the machines he 

 used, nor the relative economy of the different types of 

 engines, nor the evaporative power of boilers. He required 

 such experience as might help him to determine for him- 

 self, or at least to see for himself how other people had 



