126 PRACTICAL BOTANY 



whole space within the seed-coat, will then be disclosed : it is 

 to be observed that there is here no tissue derived from nucellus, 

 and no endosperm, and the seed is therefore described as exal- 

 buminous : note the following parts of it : 



1. The two fleshy cotyledons, which are attached to one 

 another at their base. 



2. The conical radicle, which lies externally, and in the seed 

 has its pointed apex directed towards the micropyle. 



3. Separate the two cotyledons, and between them observe a 

 bud, the plumule, composed of numerous small plumular leaves. 



(b) Compare with the Bean the flattened seed of the 

 Cucumber or Gourd : the micropyle may be found by the same 

 means as before, at the pointed end of the seed, and close to it 

 is the small scar of the hilum : this seed is of the anatropous 

 type and is ex albumin cms. Peel off the leathery seed-coat, and 

 note the parts of the straight embryo, viz. : 



1. The radicle directed towards the micropyle. 



2. The two cotyledons ; fleshy as before. 



3. Between them the very small plumule. 



(c) Examine the ripe fruit of the Sunflower (Helianthus 

 annmis). The "seeds" sold for sowing are really fruits 

 (achsenia), including the products of development of both 

 ovary and ovule. It is a dry inferior achasnium, with narrower 

 basal, and broader apical end : at the latter is a scar, where 

 were inserted the style and other floral organs. 



Compare fruits in situ on the floral receptacle. 



Dissect off the brittle pericarp, from the anatropous and 

 exalbuminous seed, which it incloses. 



Note the delicate seed-coat, and, within this, the straight 

 embryo, of which the radicle is directed towards the micropyle 

 (i.e. towards the base of the fruit), and the two cotyledons 

 towards the apex of the fruit. 



Separate the two cotyledons, and note between them, at 

 their point of attachment together, the minute plumule. 



(d) Compare the structure of the albuminous seed of the 

 Castor oil (Ricinus communis), observing externally the hard, 

 bright, variously marked seed-coat, which has attached to it at 

 the basal end a wart-like swelling the arillus 



