INHERITANCE OF SEX IN MERCURIALIS ANNUA 
433 
made a cytological examination of the developing embryo and concluded 
that fertilization had occurred. Malte (1910), who undertook a detailed 
cytological study of the plant, found the same to be the case. 
The original mother plant that I worked with produced 66 seeds, 50 
of which germinated, giving rise to female plants. The behavior of the 
Fi plants (table i) shows great fluctuations in the number of seeds pro- 
duced. Only six Fi plants, offspring. of the mother plant, produced an 
equal or larger number of seeds, the range being from 65 to 230 seeds. The 
remaining 44 plants produced fewer, the highest number being 47, the lowest 
number i. There was no marked tendency for the offspring to resemble the 
parent in seed production. With the exception of plants nos. Ill and X, 
there is an obvious synchronism in the period of male flower production 
and seed development (see table i). 
The F2 generation females (table 3) show the same marked variation 
in seed production as the Fi generation. The total seed production was 
much lower than for the Fi generation. A total of 358 seeds was produced 
by 20 of the 39 plants grown, whereas in the Fi generation 980 seeds were 
produced by 26 plants of the 50. The offspring of plant no. VII in no in- 
stance showed the tendency to profuse seed production which characterized 
the parent (table 4). 
Altogether, including the seeds of the Fi, F2, and F3 generations, 1918 
seeds were sown, producing 471 offspring all of which were female. 
Bitter {I.e.) noted that small insects, such as ants and plant lice, are 
attracted to the female flowers by the two nectaries that are present. 
Weiss (1906) made this observation earlier on the same form. Strasburger 
(1909a) estimates one thousand pollen grains for each anther, so that the 
possibility for the pollination of many female flowers by one male flower is 
great. I found that by keeping the plants separate, so that no parts 
touched, there was little danger that insects would spread the pollen from 
one plant to another. On the other hand, I crowded a group of my F3 
female plants closely together and they set seed profusely. They were 
permitted to sow themselves on the greenhouse bench, and as soon as the 
seedlings showed their sex they were destroyed. No attempt was made to 
count the seeds, but I was able to count 8,155 seedlings all of which were 
females. 
Inheritance of Maleness 
De Vries (190,3), in the second volume of Die Mutationstheorie, has a 
drawing of a male branch of Mereiirialis annua bearing fruit. However, 
he does not say anything about the behavior of the seed on germination. 
It was Strasburger (1910) who first reported upon the germination of the 
seeds set on male plants. Among the male cultures under his direct ob- 
servation 15 plants bore seed, the numbers of seeds ranging from 3 to 8. 
He had a total of 74 seeds from male plants. Not all, however, were ripe, 
