436 BOTANY. 



ovule becomes hardened by the conversion of parenchyma 

 into sclerenchyma, thus forming the testa ; in other cases it 

 becomes more or less pulpy, as in Magnolia, Pmonia, etc. 

 The outer coat is liable to be much modified in form also, 

 being sometimes developed into thin wings, or a tuft or 

 covering of hairs, as in Bignonia, Asclepias, Gossypium, etc. 

 The inner coat usually undergoes little change, generally be- 

 coming thin and dry. The ovary in many cases becomes 

 hard and dry — e.g., in Cupuliferse and Leguminosse ; in 

 others it is more or less pulpy, as in the Cherry, Plum, 

 Blackberry, etc. Both ovule and ovary at maturity (now 

 called seed and pericarp respectively, and the latter, with all 

 its contained seeds, the fruit) spontaneously separate from 

 their supporting parts, by the breaking away of the walls of 

 certain layers of cells. 



The development of the flower as a whole, or, as it is termed, the Or- 

 ganogeny of the flower, is an important and instructive subject of 

 study. The law of greater structural similarity in the earlier stages of 

 organisms becomes very evident when « e look carefully into the de- 

 velopment of flowers. Very many flowers which, when fully formed, 

 have little resemblance to each other, are found to be exactly alike in 

 their earlier stages. Relationships are thus indicated where they 

 would otherwise hardly be detected. 



Without entering further upon this subject, which would require 

 several volumes for its full treatment, it need only be said here that 

 all the floral organs are essentially alike in form and structure upon 

 their first appearance; the sepals, petals, stamens, and pistils appear 

 at first as small papillae, and it is only after they havefrrown somewhat 

 that the nature of the nascent organ can be determined by its shape. 

 Moreover, it is found (as has so often been seen in the development of 

 animals) that the rudiments of some organs which are wanting in the 

 fully-formed flower are present in its earlier stages, a fact of no less 

 significance in the comparative anatomy of plants than of animals. 



The general ai)pearance of the parts of the very young flower, and 

 their development, are well shown in the accompanying figures from 

 Hofmelster (Figs. 311-313).* 



Glossology of Angiosperms. — The great number of species of An- 

 giosperms and the multitude of forms assumed by diflfereut parts of 



* The student who wishes to study this subject further may profit- 

 ably consult Hofmeister's " Allgemeine Morphologie der Qewachse," 

 Leipsig, 1868, and Payer's "Organogenie de la Fleur," Paris, 1857. 



