286 



DICOTYLEDONOUS EMBIIYO. 



in consequence of the intimate union which takes place between 

 the two as indicated by the dotted line, c. The union between the 

 cotyledonary leaves may continue after the young plant begins to 

 germinate. Such embryos have been called pseudo-monocotyledonous 

 (\]/fvlvjs, false.) When there are two cotyledons, they are opposite to 

 each other. In some cases there are more than two present, and then 

 they become verticillate. This occurs in Coniferas, especially in the 

 Fir (fig. 508), Spruce, and Larch, in which six, nine, twelve, and even 



2 



506 507 508 



fifteen have been observed. They are linear, and resemble in their 

 form and mode of development the clustered or fasciculated leaves of 

 the Larch. Plants having numerous cotyledons are occasionally deno- 

 minated polycotyledonous. Duchartre thinks that the multiple cotyle- 

 dons of the Firs are not verticillate, but occur in two opposite groups, 

 placed like two ordinary cotyledons. Hence he considers the plants 

 to be truly dicotyledonous, with the cotyledons deeply divided into a 

 number of segments. Between the two cotyledons there is a slit which 

 is well seen in Pinus Pinaster and excelsa. Thus, the arrange- 

 ment of the cotyledons follows the same law as that of the leaves in 

 dicotyledonous or exogenous plants, being opposite or verticillate 

 according to the mode of formation of the axis. 



599. The texture of the cotyledons varies. They may be thick, as 

 in the Bean, exhibiting only slight traces of venation, with their flat 

 internal surfaces in contact, and their backs more or less convex; or 

 they may be in the form of thin and delicate laminae, flattened on both 

 sides, and having distinct venation, as in Kicinus (fig. 509), Jatropha, 

 Euonymus, &c. In the former case they are called fleshy, or seminal 

 lobes ; in the latter, foliaceous, or seminal leaves. 



600. Cotyledons are usually entire and sessile. But they occasionally 



Fig. 506. Embryo of Hiraea Salzmanniana, cut vertically, to show the inequality of the two 

 cotyledons, one of which, c, forms almost the whole mass of the embryo, d, The small cotyle- 

 don, g, Gemmule or plumule, r, Radicle. 



Fig. 507. F " 

 the distinctioi 



c, Cotyledons, which are numerous; the plant being polycotyledonous. 



