3«4 



PART IV. — VEGETABLE TAXONOMY. 



are more liable to branch, and the carpels are more likely to 

 deviate from the numerical plan of the flower. 



The embryos of Dicotyledons are also relatively large and 

 well developed. They may be associated in the seed with a 

 copious endosperm, as in the Spurges, Umbelworts and Polygo- 

 nums, or with one which is relatively small in quantity, as in the 

 Mints and Milkweeds, or the endosperm may be completely 

 absorbed before the seed is ripe, as in the Oaks, Cucumbers, 

 Roses and Cresses. In nearly every case it is formed copiously 

 at first, and usually by internal cell-formation within the embryo- 

 sac ; it may or may not be completely absorbed before the 

 seed is ripe. It is rarely the 

 case that the embryo is very 

 rudimentary in the ripe seed, 

 except in chlorophylless par- 

 asites and saprophytes, such 

 as Monotropa and the Oro- 

 banchaceae, where it often 

 consists of a cluster of only 

 a few cells. In the seeds 

 of other species, cotyledons, 

 caulicle, radicle and plum- 

 ule, are usually distinguish- 

 able. The plumule, though, 

 is sometimes wanting, even 

 in embryos otherwise well 

 developed, being represent- 

 ed only by the naked apex of 

 the caulicle rising between 

 tne bases of the cotyledons, 

 as in the species of Cucur- 

 bita. The embryos, in nearly 

 all cases, are strictly dicoty- 

 ledonous, but, in a few instances, as already explained in Part I, 

 they become falsely monocotyledonous or falsely acotyledonous 

 by the abortion of one or both of the cotyledons, and it rarely 

 happens, on the other hand, that a plant which ordinarily pro- 

 duces a dicotyledonous embryo, develops one with three. This 

 has been known to occur in the Oak and Almond. 



Fig. 578. — Ricinus communis. A, ripe seed 

 laid open longitudinally ; s, testa ; e, endo- 

 sperm ; c, cotyledon ; he, hypocotyledonary 

 part of caulicle ; x, strophiole or caruncle. B, 

 germinating seed with the cotyledons still buried 

 in the endosperm, e; tv, primary root ; iv 1 sec- 

 ondary roots. After Sachs. 



