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 /jl. 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 
