16U 



MEMOIRS OF THE XEW YORK BOTANICAL GARDEN 



temperature on the flower mechanism and the time relations of 

 the reactions. 



It would ajDpear from observing the action of the flowers that 

 the movements of the parts involve chiefly changes in turgor 

 ^vith. perhaps some actual growth of certain parts. The coordi- 

 nated action of sets of flowers does not necessarily imply that 

 there is a regulation by internal stimuli. It may only involve an 

 identity in the constitution and condition of the many flowers 

 which mature in each set. But in the repeated synchronous ma- 

 turity of sets there would seem to be a very fundamental coordi- 

 nation in the growth and develoi^ment of flowers throughout the 

 entire plant. 



Each flower normally exhibits two different actions. The 

 mechanism of the first opening and the mechanism of the second 

 opening operate under different external stimuli. The same 

 stamens which reflex strongly in the first anthesis stand nearly 

 erect in the second anthesis, but in the interval between they 

 grow^ noticeably. The same segments of the perianth open and 

 close in quite the same manner in both openings but they reflex 

 more strongly and for most varieties close more tightly in the 

 first opening. The pistil evidently usually matures during the 

 period of the first oj^ening, which is when the inner set of nec- 

 taries excrete nectar. The outer set of nectaries functions at the 

 time pollen is shed. The two sets of nectaries are, how^ever, quite 

 different in appearance. Those of the inner set resemble 

 aborted stamens; those of the outer set are shorter and more 

 rounded and dome-shaped. 



In both groups of varieties {A and B), the flowers are appar- 

 ently identical in general morphology and in the mechanism of 

 each of the two openings. Yet the conditions of light, temiDera- 

 ture, and humidity of the forenoon or of the preceding hours 

 bring into simultaneous opening first-period flowers on A varie- 

 ties and second-period flowers on B varieties and the midday 

 brings a shift of sets in each in the reverse order. Such decided 

 and specific differences in action can only be due to differences 

 in the inlierent constitution of the two groups of varieties. 



