IOO 
Peirce.— The Dissemination and 
Some of the material used was alcoholic, but always controlled by the 
examination of fresh. The fresh material was studied out of doors in the 
Arboretum and in the forest, and in the Hopkins’ Seaside Laboratory at 
Pacific Grove, as well as at Stanford University. I had fresh material sent 
to me repeatedly from Pacific Grove at times when I was unable to go 
there. The study of the dissemination and germination of this parasite 
must include the observation of the climatic conditions under which the 
plant lives, especially the humidity of the air. At Stanford University, 
which is three miles from San Francisco Bay, and cut off from the ocean 
winds by mountains ranging from 1,000 to nearly 3,000 feet in height, the 
air is much drier and the winter temperature lower than at Pacific Grove, 
which is on the Bay of Monterey, and is only a mile from the open sea. 
Though in both places the rainy season is only from October to April, the 
rainfall is heavier at Pacific Grove than at Stanford University. The 
winter temperature at Stanford University is considerably lower than on 
the coast, where in most places frost occurs scarcely oftener than once in a 
decade. There was no frost this last winter. On the other hand, the 
summer temperature of Stanford University is decidedly higher and the air 
dry, while the coast is cooler and likely to be buried in fog. Fog prevails 
on the coast during much of the time when the fruits are ripening, while 
further inland it occurs only at night. When the fruits are ripe the com- 
paratively humid air of the coast keeps them from drying. When rain 
comes in addition their water content is still greater. But further discus- 
sion of the relations of climate to this plant may be deferred for the 
moment. 
Dissemination. 
Arceuthobium occidentale flowers from September to January: in a 
year from that time the fruits are ripe. If heavy rain and high wind come 
at this time, all or nearly all of the fruits are shaken off ; the plants may 
even be broken to pieces, for they are brittle, and hence the whole crop of 
two seasons’ growth may be destroyed. In some years I have been unable 
to get fruits after mid-November. This current year, however, I found the 
fruit very abundant in the woods at Pacific Grove in the Christmas holidays 
(1903-4 
It is well known that the fruits of Arceuthobium are explosive. Before 
passing to a description of the anatomy and mechanics of the explosive 
fruit, I should like to call attention to the conditions under which the fruits 
were disseminating the ‘seeds’ at Christmas time, 1903. 
The weather was showery, but whether the sky was overcast, with or 
without rain falling, or whether the sun was shining, the air was damp and 
the temperature mild. In the woods at Pacific Grove the air was still 
