1913] YORK—DENDROPHTHORA 209 
however, is not a mere vegetative one, but is potentially distinct 
from all other nuclei in the sac. The functional nucleus in the 
sac of D. opuntioides occupies the position of an egg in the usual 
type of embryo sac. It is different from a diploid egg in that it 
does not give rise directly to an embryo. It may thus be regarded 
as a pseudo-egg and the tissue developing from it may be considered 
a proembryo or pseudo-endosperm. Owing to the very wide range 
in meaning of the term endosperm, it is perhaps allowable to 
designate the proembryo as endosperm, although it is not endo- 
sperm in the strict sense. TrevB in his studies on Balanophora 
elongata found that one of the polar nuclei gives rise to a mass of 
tissue which is quite similar to the proembryo described above. 
He called this body endosperm. The embryo arises from one of 
the central cells of this body as in Dendrophthora. He asserts that 
the embryo is apogamous in origin. Lorsy arrived at the same 
conclusions from his studies on Balanophora globosa. WINKLER 
—. with TREvB, designates this mode of origin of the embryo 
as “somatic apogamy,” since the nuclei of the endosperm possess 
the diploid number of chromosomes. WINKLER applies this same 
term to the mode of origin of the embryo, for example i in that of 
the Lastrea pseudo-mas var. polydactyla Dadds, in which the 
embryo arises by a budding out of the prothallus. Since in D. 
Opuntioides, as well as in Balanophora, the embryo does not arise 
directly from the gametophyte, it may be spoken of as pseudo- 
apogamous in origin. 
The fact that there is a fusion of two nuclei in the sac of D. 
gracile preceding the formation of the proembryo is presumptive 
evidence that warrants the assumption that reduction has taken 
place in the formation of the megaspores. The nuclei of the sac 
have thus the haploid number of chromosomes. The nucleus 
occupying the position of an egg may or may not be capable of being 
fertilized. The two nuclei which occupy the position of polar 
nuclei are, as in D. opuntioides, derived from the same nucleus. 
Such a fusion of sister nuclei is a phenomenon of unusual occurrence 
among plants. It is not unknown among animals. BRAUER (3) 
has shown that in the majority of parthenogenetic eggs of Artemia 
salina only one polar body is formed; a second one is occasionally 
