TJRTICACE.E 491 



on the ventral aspect of the seed in the folds of the embryo. 

 The latter occupies the dorsal aspect round which it is curved 

 with the radicle incurved and abutting with its tip against 

 the ventral aspect. The cotyledons are broadly oblong, deeply 

 emarginate or bifid at the apex, more or less folded transversely 

 and also deeply infolded at the apex in order to accommodate 

 themselves to the interior of the seed. The apical fission facili- 

 tates the folding. They are trinerved in the lower half, and 

 while yet in the seed auricled at the base, but by subsequent 

 growth they become euneate. 



A fourth type is met with in Hurnulus, which has a spirally 

 coiled embryo. The seed is nearly globular, but slightly 

 elongated at either end, and contains in H. japonicus a small 

 quantity of endosperm alongside the tip of the radicle and 

 a smaller portion in the centre of the coiled embryo. The 

 radicle is terete and considerably elongated. The cotyledons 

 are incumbent, and the inner has one coil more than the outer 

 so that after germination they are of equal length. The 

 outer one makes about two complete coils, and the inner one 

 three coils. The seed of H. Lupulus is exalbuminous ; the 

 embryo is coiled in a similar way to the last. When spread 

 out the cotyledons in both cases are linear and plano-convex, 

 or more or less compressed in the middle according to the 

 pressure to which the different portions are subjected. 



Seedlings. About seven different types of cotyledons have 

 come under my observation. The simplest type occurs in 

 Conocephalus niveus (fig. 649) which has very small, orbi- 

 cular, petiolate cotyledons. The first pair of leaves are very 

 small, ovate and entire ; the second pair are roundly ovate 

 and slightly toothed near the top and trinerved ; the third 

 pair are cordate-ovate, trinerved and serrate. 



The cotyledons of Urtica dioica are somewhat larger than 

 those of the last, rotund, emarginate, pubescent above, tri- 

 nerved and petiolate. Laportea urens is somewhat similar but 

 has larger cotyledons showing a midrib only. The first leaf 

 is roundly ovate ; the second much larger, cordate and inserted 

 almost on the same level ; the third is similar to the last 

 but larger. The cotyledons of Girardinia palmata (fig. 651) 

 are comparatively large, obovate-rotund, emarginate, trinerved 



