XVUl RUDIMENTS OF BOTANY. 



168. The integuments are called collectively testa, and consist of mem- 

 branes resulting from the sacs of the ovule. These membranes are called 

 by various names. 



169. Between the integuments and the embryo of some plants lies a sub- 

 stance called the alhtinen or pensperm ; the nature of this is of great im- 

 portance. 



170. The albumen is sometimes fari7iaceous or mealy, as in the Grasses ; 

 coriaceous and almost cartilaginous, as in many Umbeliferae ; mminated or 

 wrinkled, as in the Anonaceae ; horny, as in the Coffee-bean ; oily, as in the 

 Poppy ; or thin and membranous, as in many Labiatae. 



171. The embryo is the organized body that lies within the seed, which is 

 destined to become a plant similar in all respects to the parent. It is usually 

 solitary in the seed, but occasionally there are two or several. 



172. The embryo consists of the cotyledons, the radicle, the plumule and 

 the neck. 



173. The cotyledons represent the undeveloped leaves. 



174. The plumule is what is destined to become the stem, and is therefore 

 a rudimentary leaf-bud. 



175. The radicle is the rudiment of the root, and by germination becomes 

 the root. 



176. The neck or coLlum is the line of separation between the radicle anc 

 the portion above it. 



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



178. Plants that have but one cotyledon, or if with two, one of them is 

 alternate with the other, are termed MonocotyUdonous. These are also En^ 

 dogenous plants. 



179. Plants that have two cotyledons placed opposite each other, or a 

 greater number placed in a whorl, are called Dicotyledonous. These are 

 also Exogenous plants. 



180. Plants that have no cotyledons, are said to be Acotyledonous. But 

 this term is only applied to cellular plants, which Saving no stamens and 

 pistils, can have no seed. 



181. When the radicle is so bent that it touches the back of one of the 

 cotyledons, it is said to be dorsal, or the cotyledons are said to be incumbent. 



182. When the radicle is applied to the edge or cleft of the cotyledons, it 

 is said to be lateral, or the cotyledons are said to be accumbent. 



183. When the seed is called into action, germination takes place and 

 growth commences. 



