THE INFLORESCENCE, AND THE FLOWER 



271 



Such examples serve to show that meiomery by abortion may affect anv 

 of the series of parts, and not [infrequently more than one of them in the same 

 flower. It is probably the cause of greater divergence of detail in flowers 

 than any other factor. 



The most important cases of meiomery are those where one or other 

 of the essential organs may be wholly abortive. It frequently occurs 

 that flowers typically hermaphrodite may be staminate or pistillate, by 

 abortion of one or other of the essential parts. A good example is 

 seen in Lychnis dioica (Fig. 194). The Pink family to which it belongs 

 have usually hermaphrodite flowers ; but here the species is dioecious, 

 which means that some plants have only staminate others only 

 pistillate flowers. An examination of each of them shows that in the 

 staminate flowers an abortive gynoecium occupies the centre (iv.) ; in 

 the pistillate flowers ten staminoides, or abortive stamens, surround 

 the base of the ovary (ii.). Since these parts correspond in position 

 to the parts normally present in allied plants, they indicate that 

 L. dioica is dioecious by abortion. There is evidence that this form 

 of reduction has been of frequent occurrence in the evolution of 

 Flowering Plants. 



Such results are sometimes seen in extreme form, and nowhere better than in 

 the Spurge. Comparison indicates that the Euphorbiaceae are related to the 

 Geranium Family, members of which are 

 typically hermaphrodite. Some of the Spurge 

 Family [e.g. Andrachne, Phyllanthns) have 

 calyx and corolla represented, but only 

 stamens or carpels, never both. Others 

 show steps of further reduction of floral 

 structure, till in Euphorbia itself the staminate 

 and pistillate flowers reach a very simple 

 condition. The former appear as a single 

 stamen, with a ring half way up its stalk. 

 This represents the abortive perianth. The 

 pistillate flower consists of three coherent 

 carpels, with a rim below, which represents 

 again the abortive perianth (Fig. 178, p. 256). 

 The facts justify the conclusion that there 

 is here a very advanced state of meiomery. 

 Such extreme reduction is usually connected 

 with a close crowding of numerous flowers FlG 



into an aggregated inflorescence. Vertkal section o{ flower o{ Mymmm 



as an example of an hypogynous flower. 



(vi) Various development of the floral (After Figuier.) 

 axis or receptacle accounts for very con- 

 siderable differences of floral construction. As a rule the parts of 

 the flower are closely packed upon the shortened and distended 



