1918] WEIR—RAZOUMOFSKYA 21 
4-parted purple flowers, solitary or clustered, simple or branched, 
according to age of infection, bloom and fruit in the same season; 
and size of fruit, flower, plant, and color of stems show some varia- 
tions under different conditions of growth. Cross inoculations 
involving these forms should demonstrate whether or not all 3 
are identical with R. Douglasii. The results of a series of cultures 
are given in tables III andIV. | 
At the time these cultures with R. Douglasit and R. Douglasii 
abietina were made seeds of the form on Picea were not available. 
The plant is not morphologically different from the other two, and 
cultures now under way indicate that it will infect Abies and 
Pseudotsuga. The evidence so far obtained is so pointedly in 
favor of the view that all 3 forms are identical that there can 
be little room for doubt. We find, for instance, that R. Douglasii 
will infect Abies grandis, A. lasiocarpa, and A. concolor, which are 
hosts for R. Douglasii abietina. No marked morphological differ- 
ences are found in the resultant plants and their parents, any more 
than is to be expected from a change of host or condition of growth. 
The same is true for the culture of this mistletoe on Picea Engel- 
manni. The evidence that all 3 forms are identical is further 
strengthened by the fact that R. Douglasit abietina from Abies 
lasiocarpa will infect Pseudotsuga taxifolia and Abies grandis, 
and that it is possible to fertilize the pistillate flowers of this form 
on the latter host with pollen from plants on Pseudotsuga. These 
results demonstrate the relationship of the 3 small purple-flowered 
forms here considered. The two forms on Abies and Picea should 
be considered identical with R. Douglasii in view of the foregoing 
results. It has already been pointed out that, in the writer’s 
experience, the plants on Abies and Picea are in most cases found 
in localities where R. Douglasii abounds. If the former were 
specifically distinct, with inherent tendencies to select their par- 
ticular hosts, they should in the light of our knowledge of the well 
defined species be more abundant. On the contrary, they are never 
found in any quantity. The conclusion that R. Douglasii does not 
abundantly infect other trees than Douglas fir is also shown by 
the following observations. The writer has looked several times 
in vain for infection of this species on Abies and Picea when the 
