696 MR JOHN MCLEAN THOMPSON ON 



of the perianth at this stage showed that the lateral zygomorphy, so pronounced in the 

 earlier stages, had been greatly reduced. 



Its maximum reduction or complete obliteration was accomplished as the flowers 

 expanded. 



The condition of the perianth in its earliest stages will not be described in detail at 

 present, but it should now be stated that, in the flowers which were examined, lateral 

 zygomorphy was initiated in the perianth while the androecium was still actinomorphic. 



An examination of buds and expanded flowers of Greyia Sutherlandii provided, then, 

 the following facts. At a very early stage the perianth was laterally zygomorphic, the 

 androecium was actinomorphic. Soon, however, antero-posterior zygomorphy appeared 

 in the stamens, and the initiation of lateral zygomorphy followed. By this time the 

 petals had greatly outgrown the sepals, and their lateral zygomorphy had attained its 

 maximum. The zygomorphy of the corolla was greatly reduced or obliterated as the 

 flowers expanded, but the staminal zygomorphy was accentuated. This staminal zygo- 

 morphy likewise reached a maximum, and was in turn reduced, as anther dehiscence 

 advanced. 



In fig. 1 an expanded flower, borne high on the raceme, is represented. It is 

 viewed from the posterior left side. The perianth is but slightly zygomorphic. The 

 second-longest stamen is the anterior one ; the shortest, the -posterior stamen. The 

 longest stamen is second to the right of the anterior one. Its anther has dehisced, and 

 its filament has reached its maximum length. Fig. 2 represents the same flower in 

 outline, and a dotted line has been drawn touching the anthers of the five stamens 

 which formed the anterior group in the early stages of the bud. The stamen to the 

 right of the posterior one is slightly shorter than the anterior stamen, and its anterior 

 neighbour almost equals in length the third-longest stamen of the anterior group. 

 The extreme left stamen of the posterior group is almost equalled in length by the 

 left neighbour of the anterior one. It will be remembered (figs. 3, 4, 5) that at an 

 early stage in the bud the slioi^test stamens of the anterior group possessed filaments 

 of greater length than those of the longest posterior stamens. But in the expanded 

 flower the majority of the posterior stamens are, at this stage, superior in length to the 

 shortest anterior stamens. 



Fig. 6 represents a later stage. The flower is viewed adaxially. Practically no 

 elongation has taken place in the posterior stamen, but the anterior stamen, and its 

 neighbour on the right, have reached the maximum length — previously attained by 

 the extreme right member of the anterior group — and their anthers have dehisced. 

 The stamen to the right of the posterior one has almost attained its maximum length. 



Fig. 7 represents the same flower in outline, and a dotted line has been drawn, 

 touching the anthers of the five posterior stamens. 



So far, anther dehiscence has been confined to the anterior group. 



While these changes were taking place in the androecium, the style had been elongat- 

 ing, and, at the stage about to be described, its top portion had curved slightly to the 



