350 Olive.— Sexual Cell Fusions and Vegetative 
While I believe, with Christman, that the two fusing cells in the 
Caeomas are approximately equal, I think that his conception as to the 
relative position of the two gametes in these forms, as well as their equality, 
should be somewhat modified and broadened. In all of Christman’s 
figures showing the sexual fusions the two gametes are placed upright and 
parallel to each other. In my figures illustrating the process (Figs. 26-40) 
the two cells are seen to occupy various positions to each other. Sometimes 
the gametes are side by side and parallel ; while, perhaps even more often, 
one appears to be placed below the other, and seems to come up from 
below at varying angles. Christman further represents each of the fusing 
gametes as possessing a sterile cell as its tip (see, e. g. his Fig. 4, ’ 05 ), 
although the evidence, after a mutual examination of his preparations 
by the author and by myself, has not convinced me that he is right on this 
point. Wherever a sterile cell is shown in my figures (Figs. 26-28, 31, 33, 
37, 38, 40), but one gamete is seen to possess such a cell ; whereas the 
lower gamete in these preparations apparently lacks entirely this structure. 
These observations tend, therefore, to confirm in this one respect those 
of Blackman, in that he found one gamete only bearing a sterile cell as its 
tip. It will be remembered that the latter ingeniously suggests that this 
two- celled structure is a female reproductive organ, the upper sterile cell 
of which he regards as the now functionless trichogyne, while the lower 
cell retains its primitive character as a sort of egg, or ‘ female cell ’, which 
is fertilized by what Blackman terms a ‘ vegetative cell ’ from below. 
Blackman points out that the * sterile cell ’ sometimes pushes up as a long 
slender growth between the epidermal cells, thus suggesting, in his opinion, 
its primitive function when it once pushed its way to the surface and there 
served as a trichogyne to bring the spermatium into relation with the 
female cell below. 
While I agree to some extent with Blackman’s observations of facts, 
I think that a much simpler interpretation should be applied to such 
structures than that proposed by him. I should agree with him that 
but one of the two gametes ordinarily bears a sterile cell, since I have 
never found convincing evidence that both the fusing cells were thus 
equipped, as maintained by Christman. In Triphragmium sometimes two 
such cells will be found in a row at the top of one of the gametes. But 
whether sterile cells are necessarily present, or whether, on the other hand, 
they may sometimes be altogether absent, as might be inferred from those 
drawings of cell fusions in which they are not shown (Figs. 32, 34-36, 39), 
I am not prepared to say. I believe, however, as indicated above, that 
in all the caeoma type of Rusts examined by me such a sterile cell is 
generally present at the tip of one of the gametes. Further study of the 
pseudoparenchyma in the aecidium-cup type will probably assist materially 
in the interpretation of these sterile cells, since the pseudo-parenchyma 
