I20 BOTANICAL GAZETTE [august 



obser\-ed in microspores artificially removed from indehiscent 

 anthers. Very feeble germination was also obtained in tests of 

 large sized grains from fully dehiscent anthers, as in no. 25. In 

 many plants completely sterile stamens retain some suggestion 

 of filaments and anthers in regard to the general form, but all 

 traces of such differentiation may disappear, giving only foliose 

 structures as shown in nos. 10, 34, and 35. In general, the 

 various grades of development of stamens may well be regarded 

 as indicating different grades of maleness. 



In the case of all plants the flowers of which have here been 

 described and illustrated, observations were made of flowers in 

 numerous heads throughout at least one season of bloom. Some 

 have been under observation for several years. At the extreme 

 tip of the spikes in many plants there is a tendency for flowers 

 to develop poorly; the pistils usually protrude, but the. stamens 

 are poorly formed and often flowers fail to open. This is the 

 tendency to gynomonoecism especially emphasized by Schulz (24) 

 and CoRRENS (4). This tendency is evidently more marked in 

 some plants than in others, but I am unable to make any classi- 

 fication on this basis. For the plants already discussed the flow- 

 ers were very uniform for at least four-fifths of the spikes, as 

 indicated in the spikes (excepting no. 55) shown in pi. 13. 



GRADES OF INTERSEXUALISM 



Variations in the development of stamens in the same flower 

 or among sister flowers are frequent for many plants. In such 

 cases there are various mixtures of different types of flowers and 

 stamens. Some of these may be noted as follows: 



No. 36 (fig. 36). — For this plant .some stamens were nearly 

 identical with those of the first form, while others were quite as 

 in the second form. Differences in the length of stamens in a 

 single flower were conspicuous. Some anthers failed completely 

 to dehisce, while others dehisced fully. The greater portion of 

 the pollen was impotent. Grains of large size were present and 

 some of these from dehiscing anthers germinated well in cultures. 



No. 37 (figs. 37, 38, 52). — As in the plant previously noted, 

 there is much variation in the length of filaments among stamens 



