1913] YORK—DEN DROPHTHORA 207 
in the nuclei of the endosperm. From these facts it is clearly evi. 
dent that fusion of the polar nuclei in D. gracile indicates that the 
nuclear behavior in the origin of the female gametophyte is the 
same as in an ordinary sexual plant. 
Discussion 
The embryos of D. opuntioides and D. gracile arise asexually. 
In the former, reduction division does not occur preceding the 
formation of the gametophyte, the nuclei of which thus contain 
the diploid number of chromosomes. The gametophyte is apospor- 
ous in origin. Examples of apospory in seed plants have been 
described by Jue (16) in Antennaria alpina, by MuRBECK (22) 
and STRASBURGER (32) in certain species of Alchemilla, by TREUB 
(34) in Balanophora elongata, by OvERTON (27) in Thalictrum 
purpurascens, by Lotsy (19) in Balanophora globosa, by OSTENFELD 
(25, 26), ROSENBERG (29, 30), and MuRBECK in species of Hiera- 
cium, by WINKLER (40, 41) in Wikstroemia indica, and by Raun- 
KIAER (28), MuRBECK (23), and JuEt (17) in a number of forms of 
Taraxacum. Apogamy is associated with the aposporous origin 
of the gametophyte in these forms. In each of these plants, with 
the exception of Balanophora, the embryo arises from what is to 
external appearances an egg. From a cytological point of view 
the studies of SrRASBURGER and WINKLER are the most important. 
The former regarded the cell giving rise to the embryo as a sporo- 
phytic cell, since it possesses the diploid number of chromosomes. 
According to this view the embryo may be said to develop by 
vegetative budding. STRASBURGER regards the process as a case 
of apogamy and not parthenogenesis as some authors claim. He 
defines an egg as a cell having the haploid number of chromosomes 
and capable of being fertilized. 
WINKLER disagrees with STRASBURGER in regard to the use of 
the terms apogamy and parthenogenesis and the theoretical sig- 
nificance of the chromosomes. According to him, apogamy is the 
origin of a sporophyte from some cell or group of cells of the game- 
tophyte other than the egg. He uses the term parthenogenesis 
to indicate the formation of an embryo, developed without fertiliza- 
tion, from a cell having the position of an egg, whether the nucleus 
