Feb., 1923] STOUT ALTERNATION OF SEXES 6l 



(pistils and stamens) when fully developed are large and conspicuous, and 

 it is easy to observe variations in the degree of their development. The 

 petals were removed from the flowers shown in Plate VI. 



The three flowers shown in figure 2, Plate VI, were situated in a raceme 

 in the succession shown and illustrate the range seen for the plant on 

 the particular date when the photo was made; all the flowers were fully 

 and very uniformly male; but the pistils were either normal and functional 

 as in a, decidedly aborted and functionless as in c, or less conspicuously 

 aborted as in b. On the particular date the flowers were varying in respect 

 to femaleness. On other dates, however, maleness was quite as variable. 



Maleness is well developed in all the flowers shown in figure 3, although 

 the filaments vary in length and there is one stamen fully aborted in b and 

 one in c. The pistils vary from the highly developed and functional as at 

 a to the extremely aborted as in d. Figure 4 represents flowers of the same 

 plant a few days later, showing extreme abortion in stamens of some flowers 

 and some variation in the size of pistils, although all pistils were functional. 



The pistils of the various flowers shown in figure 5 are either well devel- 

 oped (a, b, and c), or decidedly aborted (d, e, and/). The development of 

 stamens is very irregular, and the extremes are seen for a single flower in 

 the various grades as to length of filament and size, development, and 

 dehiscence of anthers. Such irregularities as these are frequently seen, and 

 for numerous plants the condition was more or less present throughout the 

 period of bloom, with, however, no pod production for the flowers that had 

 only aborted pistils. 



Figure 6 shows two typical flowers of a plant on a date when the flowers 

 could function only as females. 



The four flowers shown in figure 7 show grades of abortion in both 

 pistils and stamens and illustrate very well how the abortion tends to be 

 one-sided, affecting first stamens and then pistils. 



The many controlled pollinations that were made revealed that there 

 was in these plants no limitation to fertility through physiological incom- 

 patibilities in fertilization. Every plant was highly productive of seed 

 whenever pollen of dehiscing stamens was used on well-developed pistils 

 either in self- or in cross-pollinations. Rudimentary pistils always failed to 

 set seed. Pistils over 2 cm. in length usually produced seed. 



Examination of pollen and tests for germination were made of pollen 

 from all sorts of anthers. In large, well-developed anthers, 95% or more 

 of the pollen grains appeared to be normal, and on a sugar-agar medium as 

 many as 80% often germinated, producing tubes as long as 750 n. In such 

 rudimentary stamens as at d, figure 4, only a few shriveled, empty, partly 

 developed pollen grains were present which did not even swell up when 

 placed in water. In the large-sized but indehiscent anthers of short stamens 

 as in c, figure 4, varying percentages of the pollen appeared to be normal, 

 but in no case did the pollen of such indehiscent anthers germinate when 



