1905] CURRENT LITERATURE 151 
NOTES FOR STUDENTS. 
Apocamy in the genus Alchemilla has been investigated very thoroughly by 
STRASBURGER.? The work was suggested by MuRBECK’s researches; and his 
statements that the embryo of the EUALCHEMILLAE develops from the egg without 
fertilization, and that there is no reduction of chromosomes in the life history, are 
confirmed. On the other hand, STRASBURGER reaches a different conclusion as 
to the origin of the embryo sac of apogamous species of Alchemilla, and has a 
different theory as to the nature of the embryogeny of these species. 
More than forty species were studied. In the European species the pollen, 
except in a few species, is abnormal, the development being checked at various 
stages. The pollen mother-cells may disorganize or a tetrad may be formed, but 
the pollen grains fail to be liberated from the mother-cell. In some cases, the 
division into tube nucleus and generative nucleus takes place, but such pollen 
grains disorganize early. There are thirty-two bivalent chromosomes in the pollen 
mother-cells, and sixty-four univalent chromosomes in the vegetative tissues. In 
American and African species, an examination of herbarium material showed 
normal pollen, and it is probable that fertilization occurs in the usual way. 
In the ovules of apogamous EUALCHEMILLAE one or more megaspore mother- 
cells appear. The nucleus passes through the prophases of the heterotypic 
division up to the synapsis stage, but here the mode of development changes an 
the nucleus divides by a typical vegetative division. Division in the embryo sac 
shows the sporophytic number of chromosomes, so that when the egg is formed it 
contains the vegetative number of chromosomes. When such an egg develops 
an embryo without fertilization, STRASBURGER regards the phenomenon not as 
parthenogenesis but as apogamy. Strictly speaking, it would not be even a case 
of apogamy, but we should have merely an adventitious embryo like one coming 
from cells of the nucellus. There is not the beginning of a new generation. 
The subniveal EVALCHEMILLAE which form normal pollen show a reduction 
of chromosomes in the formation of the megaspores, and fertilization takes place 
in the usual way. Those EUALCHEMILLAE which have not lost their sexuality 
are chalazogams, and some of them form hybrids. 
It seems probable that the extraordinary mutation of the EUALCHEMILLAE 
has weakened the sexuality, and that the failure of fertilization has brought on 
the apogamous condition. 
Rubus and Rosa, which were also examined, have retained their sexuality 
in spite of extensive polymorphism. The reduction division and fertilization 
occur regular 
Dioecism has in many cases given an impulse toward apogamous reproduc- 
tion, since the separation of male and female individuals decreases the frequency 
of fertilization —C. J. CHAMBERLAIN. 
ey 
7 STRASBURGER, E., Die Apogamie der Eualchemillen und allgemeine Geschichts- 
punkte, die sich aus ihr ergeben. Jahrb. Wiss. Bot. 41:88-164. pls. 1-4. 1905. 
