168 SYSTEMATIC SOTANY. 



for the future growth of the embryo is largely stored up 

 in the tissue of the ovule surrounding the embryo-sac, and 

 this tissue is called perisperm. The ovary, as well as the 

 ovule, usually undergoes great changes while the embryo is 

 forming. The outer parenchymous coat of the ovule often 

 becomes more or less sclerenchymous, and forms the testa; 

 or it may become pulpy ; in some cases it develops wings, 

 or a tuft of hairs, etc. The ovary may become hard and 

 dry, or pulpy. These two, called now seed aud pericarp 

 respectively, spontaneously separate at maturity from the 

 parent plant. 



187. The epidermis of the Angiosperms has commonly 

 more stomates than that of the Gymnosperms. The tri- 

 chomes, or hairs, are more often present, and exhibit a 

 greater variation in form and structure. The fundamental 

 tissue is abundant, and mostly parenchymous in the annual 

 stemmed species ; in the perennials there is less of it, and 

 more of the fibro-vascular tissue. In these sclerenchyma 

 is also usually developed. The chlorophyll-bearing paren- 

 chyma of the leaf (mesophyll) is fundamental tissue; so 

 also are the succulent parts of fruits. The fibro-vascular 

 bundles are either closed or open, and their disposition for 

 the most part is dependent on the position of the leaves. 

 They are usually of the kind called "common bundles," 

 that is, they extend above into the leaf, and below into the 

 stem. In a few cases there are " cauline bundles," or those 

 in the stem which have no connection with the leaf. 

 Based on the number of cotyledons in the embryo, the 

 structure of the stem, etc., the Angiosperms have been 

 divided into two sub-classes, the Monoeotyledones and the 

 Dicotyledonea. 



