SEEDS AND SEEDLINGS. 



51 



83. Endospermic Seeds. In many seeds the stored 

 food is not contained in any part of the young plant itself, 

 but in a special part of the seed called the endosperm, 

 which lies within the seed-coat but outside of the young 

 plant (embryo). In some cases the endosperm surrounds the 

 embryo (e.g. Castor Oil, Ash). In others the embryo is coiled 

 around the endosperm, e.g. Buckwheat. In Maize, Wheat, 

 and other Cereals and Grasses the embryo and endosperm are 

 sharply separated by a plane drawn across the seed. In all 

 cases, however, the radicle of the embryo is close to the sur- 

 face of the seed, just within the micropyle. 



Unfortunately the old term " albumen" is often used instead 

 of endosperm, and this sometimes leads to confusion. Endo- 

 spermic or " albuminous " seeds are seeds whose food is 

 stored in a part outside of the embryo, and this food may be 

 chiefly starch (e.g. Maize) or largely oil (e.g. Castor Oil), or 

 cellulose in the form of much- thickened cell-walls (e.g. Date). 

 The term " albuminous " does not, therefore, imply the pre- 

 sence of egg-albumin, though seeds do contain proteids, 

 and exactly the same kinds of 

 food are stored in endospermic 

 and non-endospermic seeds 

 alike. 



Note the following common 

 error (often found in carelessly 

 written books) : " the Bean seed 

 contains endosperm in its coty- 

 ledons " (what is wrong in this 

 statement ? ) . Another common 

 mistake is the generalisation 

 about Dicotyledonous and Mono- 

 cotyledonous seeds mentioned 

 in Art. 91. 



ENDOSPERM 



COTYLEDONS 

 PLUMULE 

 RADICLE 

 ARIL 



Fig. 27. Seed of Castor Oil. 



A, Longitudinal section ; B, Trans- 

 verse. The dark outline represents 

 the seed-coat. 



* 84. Castor Oil. Notice the 

 spongy mass covering one end of the 



seed ; the hard seed-coat, the oily endosperm, the embryo in the 

 middle of the endosperm, with thin cotyledons pressed together 

 (try to find root and shoot) ; cut longitudinal and transverse 

 sections. The spongy mass (aril) soaks up water ; prove by placing 

 seeds in hot water that this mass lies close to the micropyle. See 

 Fig. 27. 



