318 SIR J. LTJBBOCK — PHYTOBIOLOGTCAL OBSEHVATIOXS. 



arrangement. It must be admitted that there are some cases in 

 wMch the anatropj of the seed appears at first sight rather dis- 

 advantageous than otherwise. Most of these can, I believe, be 

 explained, Avhile iu some it is possible that the plants retain, even 

 perhaps to their present disadvantage, an arrangement inherited 

 from an ancestral condition in wliich it was beneficial. I hope,- 

 however, to enter into this more fully on a future occasion. 



When we cut open a seed, we find witliin it a more or less dif- 

 ferenliated embryo ; sometimes, as in the Ai^h. (Fraxinus, fig. 48), 

 or Castor Oil {Ricimis, fig. 51), &c., a lovely little miniature plant, 

 generally white, but in some species green, distinctly formed, 

 but still embedded in food-material or *^ perispcrm." Such phiuts 

 occupy an intermediate place between those in which, as for 

 instance in the Larkspur {DeJphiniujn, fig. 130), the embryo is 

 very small, and those, on the other hand, where, as in Ilijipoplia'e 

 (fig. 55), the perisperm is reduced almost to a film, or, as in the 

 Bean, where the embryo occupies the whole seed, and the 

 nourishment intended for the young plant is stored up In the 

 cotyledons themselves. 



In a Walnut, for instance, the two halves of the seed are the 

 two cotyledons, and attached to them may be found tl)e little 

 plantlet Avith a delicate white root, and a little stalk bearing five 

 or six minute rudiments of leaves, often just tipped with green, 



I will now pass from seeds to seedliuirs. No one who has 

 ever looked at young plants can fail to have been struck by 

 the contrast they aflbrd to the older specimens belonging to the 

 same species. This arises partly from dift'erences in the leaves, 

 partly from the contrat^t Avhich the cotyledons, or seed-leares, 

 aff^ord, not only to the final leaves, but even to those by which 

 they are iuimediately followed. 



This contrast between the cotvledons and true leaves is so 

 great that one might almost be pardoned for asking whether they 

 can be brought into actual correlation, or whether the cotyledons, 

 with the portion of stem belonging to them, might occupy some 

 such relation to the rest of the plant as the prothallium does to 

 the fronds of the Fern. 



This, however, is not the direction in which we must look for 

 the true explanation of the differences. 



So far, indeed, are tlie cotyledons from agreeing with the forms of 

 the leaves," that the difficulty is to find any which have been clearly 

 influenced by them. One species oilpomcsa (L Pescaprce) has both 



