106 Sir John Luhhoch [April 25, 



subsequent leaves. Klebs, indeed, in his interesting memoir on 

 " Germination," characterises it as quite an enigma. 



Mustard and cress were the delight and wonder of our childhood, 

 but it never then occurred, to me at least, to ask why they were 

 formed as they are. So they grew, and beyond that it did not 

 occur to me, nor I thinlv to most, that it was j)ossible to inquire. 

 I have, however, I think, suggested plausible reasons in many cases, 

 some of which I will now submit for your consideration. 



Cotyledons difler greatly in form. 



Some are narrow, in illustration of which I may mention the 

 fennel and ferula, in the stalk or ferule of which Prometheus is 

 fabled to have brought down fire from heaven. 



Some are broad, as in the beech and mustard. Moreover, some 

 species have narrow cotyledons and broad leaves, while others have 

 broad cotyledons and narrow leaves. 



Some are emarginate, as in the mustard ; lobed, as in the lime ; 

 bifid, as in Eschscholtzia ; trifid, as in the cress ; or with four long 

 lobes, as in Pterocarya. 



Some are unequal, as in the mustard ; or unsymmetrical, as in the 

 geranium. 



Some are sessile, and some are stalked ; some are large, some 

 small. 



Generally, they are green, leaf-like, and aerial, but sometimes 

 they are thick and fleshy, as in the oak, nut, walnut, peas, beans, 

 and many others, in which they never quit the seed at all. 



Let us see, then, whether we can throw any light on these difier- 

 ences, and why they should be so unlike the true leaves. 



If we cut open a seed, we find v\ithin it the future plant ; some- 

 times, as in the larkspur, a very small oval body; sometimes, as in 

 the ash or the castor-oil, a lovely little miniature plant, with a short 

 stout root and two well-formed leaves, inclosing between them the 

 rudiment of the future stem, the whole lying embedded in food- 

 material or perisperm ; while sometimes the embryo occupies the 

 whole interior of the seed, the food-material being stored up, not 

 round, but in, the seed-leaves or cotyledons themselves. Peas and 

 beans, almonds, nuts, and walnuts, are familiar cases. In split peas, 

 for instance, — who split the peas ? If you look at them you will see 

 that it is too regularly and beautifully done for human hands. In 

 fact, the two halves are the two fleshy cotyledons : strictly speaking, 

 they are not split, for they never were united. 



Narrow Cotyledons. 



Let us now begin with such species as have narrow cotyledons, 

 and see if we can throw any light on this characteristic. The pro- 

 blem is simple enough in such cases as the Plane, where we have, on 

 the one hand, narrow cotyledons, and, on tljc other hand, a long 



