54 INTRODUCTION. 
There is a possibility that this doctrine may not be applicable to 
cases of apogamy, apospory, and normal parthenogenesis among 
plants. It has been suggested by Strasburger (’94, p. 300) that the 
number of chromosomes may become doubled under the influence of 
correlative processes in an apogamously developed fern which arises 
as a bud from the prothallium, the nuclei of whose cells contain the 
reduced number, and for the same reason the reverse may take place 
in cases of apospory, z. e., the aposporous development of prothallia 
may be attended with a correlative reduction in the number of chromo- 
somes. Until the facts are determined by actual observation, all 
discussion of this subject must remain a matter of pure speculation, 
The researches of Juel (1900) upon the normal parthenogenesis of 
Antennaria alpina are of the highest interest in this connection, as 
they throw light upon this question so far, at least, as the seed-bearing 
plants are concerned. In Avztennarda alpina, in which the egg 
develops parthenogenetically under normal conditions, Juel finds that 
no reduction in the number of chromosomes takes place in the develop- 
ment of the embryo-sac, and, consequently, the nucleus of the egg- 
cell which gives rise to the parthenogenetic embryo contains the same 
number of chromosomes as the vegetative cells. Contrary to Anten- 
naria dioica, in which fecundation regularly occurs, the mother-cell 
of the embryo-sac of A. alfina develops immediately into the embryo- 
sac, the heterotypic and homotypic nuclear divisions which follow the 
appearance of the reduced number of chromosomes being omitted. 
In cases of normal parthenogenesis among the angiosperms, the 
facts, so far as they are known, are certainly not at variance with the 
doctrine of the reduction of the chromosomes as applied to the alter- 
nation of generations. e 
As has been intimated in preceding paragraphs, the sexual genera- 
tion has been spoken of as the more primitive condition, and, as will 
be seen from the following, the reduction in the number of chromo- 
somes in the spore mother-cell is regarded by Strasburger as the 
return of highly organized plants to the original unicellular condition: 
The morphological cause of the reduction in the number of chromosomes 
and of their equality in number in the sexual cells is, in my opinion, phylo- 
genetic. I look upon these facts as indicating a return to the original generation 
from which, after it had attained sexual differentiation, offspring was developed 
having a double number of chromosomes. Thus the reduction by one-half of 
the number of the chromosomes in the sexual cells is not the outcome of a 
gradually evolved process of reduction, but rather it is the reappearance of 
the primitive number of chromosomes as it existed in the nuclei of the genera- 
tion in which sexual differentiation first took place (1. c., p. 288). 
The phenomenon under consideration is essentially that of the return of the 
