MOEPHOLOGY OF THE FEUIT AND SEED 275 



this may either occur as an irregular character, or as a regu- 

 lar condition, as in many Coniferse (fig. 598, c), where we fre- 

 quently find six, nine, or even fifteen ; hence such embryos 

 have been termed polycotyledonous. In all cases where the 

 number of cotyledons is more than two, they are arranged in a 

 whorl (fig. 598, c). Xajiis, the Yew tree, has onlj' two coty- 

 ledons. 



When no albumen is present in the seed the cotyledons are 

 usually thick and fleshy, as those of the Bean and Almond {fig. 

 594), in which case they are termei fie shy ; in albuminous seeds 

 they are thin and leaf-like, as in the Lime (fig. 590, c, c), when 

 they are said to be foliaceous. The foliaceous cotyledons are 

 frequently provided with veins, and stomata may be also some- 

 times observed on their epidermis ; but these structures are 

 rarely to be found in fleshy cotyledons. Fleshy cotyledons 

 serve a similar purpose to the 

 albumen, by acting as reservoirs 

 of nutritious matters for the 

 use of the young plant during 

 germination ; hence, when the 

 albumenis absent, the cotyledons 

 are generally proportionately ^._^ ^^^^ ^„^ ^^^^,j^^ 



increased lil size. polycotyledonous em- 



bryo of a species of 

 Finns beginning to 

 germinate, c. Cotyle- 

 ilons. /'. Radicle, t. 



Tigellnm. Ficj. 699. 



Tlie embryo of On-a- 

 niiiin malle. c. Coty- 

 ledons, each of v liicli 

 is somewhat lobed, 

 and furnished with a 

 petiole, J), r. RarliclG. 



Fig. 698. 



Fig. 599. 



The cotyledons of Dicoty- 

 ledonous plants are commonly 

 sessile, and their margins are 

 usually entire, but exceptions 

 occur to both these characters ; 

 thus, in Oeraninm molle (fig. 

 599, p) they are petiolate ; while 

 in the Lime (Jig. 590, c, c) they 



are distinctly lobed ; and in the Geranium (fig. 599, c) they are 

 also somewhat divided or lobed at their ends. Their positions 

 relatively to each other also vary. Generally they are placed 

 parallel, or face to face, as in the Almond (fig. 594), Pea (fig. 

 16), and Bean ; but they frequently depart widely from such 

 a relation, and assume other positions similar to those already 

 described in speaking of the vernation of leaves and the testiva- 

 tion of the floral envelopes. Each of the cotyledons may be 

 either reclinate, cond/upUcate, convolute, or circinate. These 

 are ihe commoner conditions, and in such instances both 

 cotyledons are either folded or rolled in the same direction, so 

 that they appear to form but one body ; or in rare eases they 



