1913] VYORK—DENDROPHTHORA 201 
of 5 or 6 miles around Cinchona, Jamaica, at altitudes varying 
from 2000 to 5500 ft. above sea-level, and could find no staminate 
flowers. Microtome sections of more than 200 ovules mature 
enough to show whether pollination had occurred gave no traces 
of pollen adhering to the stigmas or pollen tubes within the tissue 
of the style. Examination of 150-200 ovules of D. gracile likewise 
failed to show pollen tubes. If pollination does occur in these 
plants, the mode of origin of the embryo and endosperm is strik- 
ingly different from anything elsewhere known. In recent studies 
on Phoradendron flavescens, the author observed near Austin, Texas, 
a single plant more than a mile distant from others of its kind, 
fruiting abundantly. The berries of this plant contained normal 
seeds. Since Phoradendron flavescens is dioecious, the chances for 
wind pollination in this case were very slight. Hence it is apparent 
that this plant was producing fruit without having been pollinated. 
In the following year a number of branches bearing pistillate flowers 
were covered with cheese-cloth bags before the shedding of the 
pollen had begun, and allowed to remain until there was no longer 
any possibility of pollination. They produced fruit as abundantly 
as the uncovered branches. Thus it is evident that in Phoradendron 
flavescens pollination is not necessary for the production of seeds. 
In fact, pollination probably does not occur in plants under natural 
conditions, for in studying sections of a few hundred young fruits 
of this species, no pollen tubes or germinated pollen were seen. 
There are 18-22 chromosomes present in the cells of the embryo 
of D. opuntioides, which is the number found at the division of the 
megaspore mother cells. There is thus apparently a constant num- 
ber of chromosomes throughout all the different stages of develop- 
ment of this plant, which seems clearly to preclude all possibility 
of fertilization. Since no nuclear fusions were seen within the sac, 
it seems evident that no reduction division has occurred previous 
to the formation of the gametophyte. Estimates of chromosomes 
made in the cells of the embryo of D. gracile show that there are’ 
18-20. The cells of the endosperm in each species contain the same 
number of chromosomes as is found in the embryo. 
It was impossible to obtain a complete series of good sections 
of the different stages in the development of the endosperm and 
