SEED 217 



the hard, bright, variously marked seed-coat, which 

 has attached to it at the basal end a wart-like swelling 

 the arillus. 



Remove the testa, which is brittle and easily cracked ; 

 note beneath this a thin papery white layer, the 

 tegmcn of old writers : this closely invests the white 

 oily mass of the endosperm, a tissue which is not 

 present at the period of maturity in any of the seeds 

 above described. Cut this through transversely : and 

 a flattened central cavity will be found, lined on either 

 side by one of the thin flattened cotyledons of the 

 embryo. Lay open the endosperm of another seed 

 longitudinally, by a cut following the plane of the flat- 

 tened cavity : it will then be clearly seen that the 

 straight embryo is embedded in a mass of endosperm, 

 and that it consists of two cotyledons, radicle, and 

 plumule. 



(e) Examine also the soaked fruits of Mirabilis: 

 these are invested by a thick rugged brown coat, which 

 is the indurated and persistent base of the perianth : 

 the pointed end is the apex, the flattened end the base. 

 Remove this outer coat, and the light-brown achene 

 will be found covered by a thin double investment 

 which represents the pericarp and seed-coat : through 

 this the form of the curved embryo can be distinguished, 

 especially the radicle, at the tip of which (i.e. at the 

 base of the achene) will be seen the scar or hilum, 

 while at the opposite or upper end a little brown wart 

 represents the insertion of the style. 



Remove the pericarp and seed-coat, and observe the 

 embryo curved round, and inclosing a central mass 

 of mealy endosperm. Recognize the parts of the 



