No. 464] STUDIES ON PLANT CELL.—VIT. 557 
(or parthenogenetically if the antipodal be considered the homo- 
logue of an egg) in Alchemilla sericata (Murbeck, :02). A sum- 
mary of the various types of vegetative apogamy, parthenogen- 
esis, and sporophytic (nucellar) budding, supplementing a list of 
Ernst (:or) is given by Coulter and Chamberlain (: 03, p. 221). 
We will now take up the few investigations which consider 
the cytological details of parthenogenesis. That of Williams 
(: 04b) on Dictyota is the only one treating of a lower type. It 
seems probable that parthenogenesis in Dictyota is in no sense 
normal and would not lead to mature plants, since the germina- 
tion of unfertilized eggs in the cultures of Williams presented 
many irregularities.. The spindles instead of being formed from 
asters with centrosomes are intranuclear in origin, multipolar, 
and very irregular in their form. As a result the 16 chromo- 
somes become scattered and a cluster of daughter nuclei is 
formed containing varying numbers of chromosomes, sometimes 
one and sometimes several. It is clear in Dictyota that the fer- 
tilization of the egg results in the development of an aster with 
a centrosome which exerts a directive influence in mitosis pre- 
venting a scattering of the 32 chromosomes and conducting the 
mitosisin a normal fashion. Williams does not believe that the 
centrosome is introduced as an organized structure into the egg 
by the sperm but that it is formed de novo as a result of the 
increased metabolic activities present in the fusion nucleus as 
compared with that of the unfertilized egg. 
There have been several important studies on parthenogenesis 
in the spermatophytes. Some of these papers while establishing 
the facts of parthenogenesis in various forms, give no details of 
nuclear history or behavior of the chromosomes. But the studies 
of Juel (: 00), Overton (:04), and Strasburger (: 04), present some 
very interesting data on the cytological features of parthenogen- 
esis in Antennaria alpina, Thalictrum purpurascens, and several 
species of Alchemilla. 
Several recent papers indicate that parthenogenesis may prove 
to be general in certain genera or even € 
groups and therefore a far more widespread phenomenon than 
has been supposed. Raunkiaer (: 03) (abstract in English in 
Bot. Centralb., vol. 93, p. 81, 1903) proved by cutting off the 
