(;rovvth and development of the inflorescence and flower 501 



scope tor new obseix'ational and experimental investigations of floral 

 morphogenesis is xirtually unlimited. As these ha\e their inception in 

 physiological and genetical as well as in morphological concepts, the 

 results should be of interest to both the causal and the taxonomic in- 

 quirer. In this section attention will be directed to some recent investi- 

 gations, and also to some old ones, which illustrate what can be 

 achieved in this field. In this work, too much emphasis cannot be 

 placed on the need for precise observation, in both vegetative and 

 floral meristems, of the apex as a whole and of the manner of develop- 

 ment of growth centers (Wardla\\', 1959). For example, some growth 

 centers (normally foliar loci) may gi\'e rise to flower buds, as in Nym- 

 pJwca and NiipJiar spp. (Figure 8); some centers may have a very 

 transitory existence and may soon be lost to view as floral develop- 

 ment proceeds, as in the case of bract development in some Nym- 

 phaeaceae ( Cutter, 1957, 1959 ) . 



Investigations relating to homology. Goethe's classical view of the 

 prototypic dicotyledon flo\\'er as a determinate shoot or axis, bearing 

 the several floral organs, which are homologous with leaves (Arber, 

 1937; Fames, 1931), is well supporte'd by recent investigations. Tepfer 

 (1953), for example, as we have ahead)- mentioned, has produced an 

 elegant histological demonstration that, at their inception in the meri- 

 stem, the lateral organs, whether of leafy shoot or flower in species of 

 Ranunciihis and Aqiiilcgia, are closely comparable and truly homolo- 

 gous. This view is also supported by the writer's concept of the apical 

 meristem and its property of giving rise to growth centers, and by the 

 J. Heslop-Harrison ( 1959 ) physiological studies of floral development. 

 On the other hand, it does not appear that alternati\e theories of 

 flower formation— e.g., those of Gregoire (1938), McLean Thompson 

 (1937) and others, including that recently advanced by Plantefol 

 (1948), Buvat (1952, 1955), and their adherents— seriously disturb the 

 classical conception as based on contemporarv theory and fact, though 

 they have undoubtedly called attention to phenomena which require 

 further investigation. The cliaracteristic heteroblastic developments 

 observed in the transition leaves, bracts, and perianth in many species 

 give realistic support to the classical concept. Obviously the concept 

 of homology should not be pushed too far, for while all the growth 

 centers in a particular species have some properties and activities in 

 common, they may differ in respect of other properties and activities, 

 yielding organs so different morphologically that excessive homologiz- 

 ing becomes absurd. In Niiphar and 'Nymphuca, for example, flower 

 buds originate from growth centers which form part of the normal 

 genetic, phyllotactic spiral and are therefore homologous with leaves 

 in this particular respect, but it would be idle to attempt to push the 

 homology further. Some inflorescences present similar difficulties. 



