512 PLANT GROWTH AND PLANT COMMUNITIES 



Biochemical investigations of floral morphogenesis, which will re- 

 quire very delicate techniques (not yet available), will evidently have 

 to be greatly extended before we come to grips with, for example, the 

 factors that determine the quantitative and qualitative differences be- 

 tween a petal and a stamen, or between a stamen and a carpel. Gross 

 analyses are unlikely to prove adequate, though they may sometimes 

 provide useful leads. And similarly, although direct treatments of floral 

 meristems with various metabolic substances, along the lines that have 

 proved feasible in Dnjopteris (Wardlaw, 1957a) will almost certainly 

 yield some interesting morphogenetic effects, it remains to be seen 

 whether such experimental procedures will increase our understanding 

 of the more fundamental phenomena of floral ontogenesis. In any 

 event, information from such sources, if it is to be of real value, must 

 be brought into relation with the associated genie action. 



To summarize: In the chemical approach to floral morphogenesis, 

 the aims are to discover what specific substances, or balance(s) of 

 metabolites, are involved in the inception of the several distinctive 

 floral organs, and to ascertain to what extent the normal pattern of de- 

 velopment can be modified at will by specific treatments. That particu- 

 lar substances are closely, and possibly obligatorily, involved in the 

 inception and development of the stamens or of the carpels can scarcely 

 be doubted, but they may be very difficult to detect. 



Evidence from surgical treatments. In surgical experiments the 

 principal aims are to obtain new information on the interrelationships 

 of the several regions of the floral meristem and of the incipient and 

 developing organs (Wardlaw, 1957c). By making use of favorable 

 materials— e.g., selected rosette plants, which can survive operational 

 techniques and are suitable for close day-by-day observation at appro- 

 priate magnifications— some new possibilities of investigating floral 

 morphogenesis lie before us. In particular, developmental phenomena 

 which are of general occurrence might well be given priority in such 

 investigations. 



In surgical experiments on Primula biilleyana, Cusick (1956) ver- 

 tically bisected the meristem at different, known stages in floral onto- 

 genesis— e.g., before perianth inception, and so on. By subsequently 

 observing whether complete or half whorls of the several floral organs 

 were formed, he was able to obtain some validation of the writer's 

 concept of the meristem as a unified reaction system undergoing a 

 sequence of changes in its organogenic activities. For example, floral 

 apices bisected up to the end of the primordial stamen stage con- 

 tinued their development as two growing regions, new organs being 

 formed between them and the incision; bisections made at an earlier 

 stage admitted of the formation of other groups of floral organs be- 

 tween the new flower center and the wound. Surgical experiments 

 along these lines might well be extended with interesting results to 



