CHAPTER 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 veiy 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 they 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 extremitj^, 

 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 

 stud}' 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 



