CHAPTEE IV. 



MINUTE STRUCTURE AND DEVELOPMENT OF THE 

 FLOWER, FRUIT, AND SEED. 



THE FLOWER. 



466. IN Volume I. Chapter VI., it has been shown that a 

 flower is to be regarded as a modified branch with very short 

 internodes and with the foliar expansions assuming forms unlike 

 those of ordinary leaves. In the outer circle the calyx the 

 parts have frequently the texture and color of foliage ; but in all 

 the other circles of the flower the} 7 are notably metamorphosed. 

 Notwithstanding their disguises, the parts of the flower are iden- 

 tifiable as leafy structures arranged upon an axis. On the care- 

 ful examination of flower-buds the homology between all their 

 parts and those of a leaf-bud becomes evident. In fact, in their 

 earliest state it is impossible to discriminate between these two 

 kinds of buds. Each has a rounded or cone-like extremity, 

 upon which are disposed at definite points the papillae which are 

 to develop into foliar organs. In one, these papillae become 

 green leaves ; in the other, the parts of a flower. 



467. Two features in the development of flowers require 

 special attention ; namely, the sequence in which the organs are 

 produced, and the order in which the histological elements make 

 their appearance. But it is not well in any given case to under- 

 take the examination of the development either of the organs or 

 of the tissues which compose them, until the student has made 

 himself familiar with the characters of the full-grown flower. 



468. Undeveloped racemes afford the best material for the 

 study of the developing organs of the flower, and it is generally 

 possible to find in a single young cluster flowers in all the earlier 

 stages of development. There are two good methods of pre- 

 paring the material for the compound microscope : (1) the whole 

 raceme, first decolorized by absolute alcohol and then softened 

 by glycerin, is to be dissected under a simple lens, and the sepa- 

 rate flowers are to be bleached with sodic hypochlorite ; or (2) the 



