SEED. 67 



567. The number of cotyledons varies from one to several. 

 The most common number is either one or two. In the latter 

 case, they are always directly opposite each other. 



The cotyledons are semiterete 895 " ; foliaceous 278 ; flat, convolute 288 ; parallel 

 with each other, or divergent 300 . When there is but one cotyledon, it often 

 assumes peculiar forms: it is, for instance, fungous 289 ; spheroidal 298 ; lenti- 

 cular 299 a. 



568. The direction of the embryo, with respect to the seed, 

 will depend upon the relation that the integuments, the raphe, 

 chalaza, hilum, and micropyle, bear to each other. 



569. If the nucleus be inverted, the embryo will be erect, 

 or orthotropous ; Ex. Apple. 



570. If the nucleus be erect, the embryo will be inverted, 

 or antitropous ; Ex. Nettle. 



571. If the micropyle is at neither end of the seed, the em- 

 bryo will be neither erect nor inverted, but will be in a more 

 or less oblique direction with respect to the seed ; Ex. Prim- 

 rose ; and is said to be heterotropous. 



572. Plants that have but one cotyledon, or, if two, with 

 the cotyledons alternate with each other, are called MONO- 



COTYLEDONOUS 293 ^ 2 ". 



573. Plants that have two opposite each other, or a greater 

 number placed in a whorl, are called DICOTYLEDONOUS 288 29 C92 



297 300 301 



574. Endogenous plants are monocotyledonous. 



575. Exogenous plants are dicotyledonous. 



576. Plants that have no cotyledons are said to be ACOTYLE- 



DONOUS 294 . 



577. But this term is usually applied only to cellular 

 plants which, having no sexual apparatus, can have no seeds 

 (587). 



578. Acrogenous plants are acotyledonous. 



579. Those seeds of flowering plants, which appear to have 

 no cotyledons, owe their appearance to the cotyledons being 

 consolidated ; Ex. Lecythis, Olynthia : or abortive ; Ex. Cus- 

 cuta. 



580. The plumule is very often latent, until it is called into 

 action by the germination of the seed. Sometimes it is un- 

 distinguishable from the cotyledons; sometimes it is highly 

 developed, and lies in a furrow of the cotyledon ; Ex. Maize 



F2 



