INHERITANCE OF SEX IN MERCURIALIS ANNUA 425 
The tendency of males to produce males is obvious. Still the fact that 
they can produce a few pistils sporadically and thus set seeds, makes it 
equally clear that sex determination is not absolute. Some plants are 
pure males, others set a few seeds. There are all grades of maleness as of 
femaleness. 
Table 8. Summary of Results of Male Cultures 
Number of 
Plants 
Number Setting 
Seeds 
Number of Seeds 
Number Without 
Seeds 
Number of Seeds 
Germinated 
Sex 
12 
2 
8 (3 lost) 
10 
I 
36 
I 
7 
35 
0 
167 
I 
2 
166 
0 
500 
29 
283 
471 
75 
& 
75 
2 
4 
73 
2 
& 
790 
35 
304 
755 
78 
Monoecious Mercurialis annua 
It has already been stated that monoecious forms of M. annua have 
been described in systematic works (Engler and Prantl, 1897). Kruger 
(1908, p. 338) reports the appearance of monoecious individuals among 
-his cultures. Bitter (1909, p. 124) observed monoecious forms. The 
twelve individuals that Bitter describes as occurring in the old Botanical 
Garden in Berlin had large male spikes. The monoecious forms I have 
been working with showed no such male characters. 
From the mixed seeds secured from the Brooklyn Botanic Garden I 
obtained a number of plants that, although in their appearance they were 
like the females, yet in the production of seeds showed a marked contrast. 
Seed production in these plants began about three months after germina- 
tion. Before this time the plants produced an abundance of female flowers 
which dropped off shortly after their appearance upon the plant. The 
plants were examined at intervals for the presence of male flowers. Four 
plants were kept under observation. A large number of male flowers was 
produced daily after their first appearance. I counted over 100 male 
flowers on one plant at one time. My work on the monoecious plants 
has not gone far enough to warrant drawing final conclusions, yet it is safe 
to assume that in the amount of seed produced there will be fluctuations 
similar to those in the female and male cultures. There are approximately 
as many male flowers as female flowers upon the monoecious individuals. 
The four plants produced seeds about the same time. The following is 
the record of seeds collected from the four on the same day. 
Plant 
1. 320 seeds 
2. ICQ " 
3. 269 
