118 MISSOURI BOTANICAL GARDEN. 
mentose species that do not show the marks of puncture, 
which indicates that a great many punctures are fruitless in 
result, owing either to the difficulty of the operation of 
oviposition, or to the fact that the eggs, having been once 
consigned to the pistil, have failed to hatch, for one reason 
or another; or again, that the larva has, for one reason or 
another, perished. A similar mortality is connected with 
the similarly difficult and complicated oviposition of the 
Cynipide, as Adler has shown. In dissecting the young 
fruits of the filamentose Yuccas, with a view to critical ex- 
amination, I have found that about half of them, on the aver- 
age, contain nothing; but the proportion varies greatly in dif- 
ferent localities and according to circumstances, and I may 
say that, as a result of my numerous examinations, fully 
two-thirds of the mature pods are found to contain the 
larve of Pronuba. All the experiments which I have so 
far made, or have known to be made, prove conclusively 
that the capsular species never set fruit without her aid. 
SELF-FERTILIZATION OF YUCCA. 
While the capsular Yuccas are thus sterile wherever 
Pronuba does not occur, or is excluded from the flowers, 
there is good evidence that some of the soft-fruited species 
have exceptionally set fruit where there is every reason to 
suppose that Pronuba does not exist. I have already shown, 
in previous writings, how the structure of the flowers of 
alotfolia renders the chance of pollination greater than in the 
other cultivated forms. There is no style, the stigma is 
sessile, and the stigmatic liquor isabundant, filling, and even 
overflowing, the shallow opening or tube. The flowers are 
always more pendulous, even in full expansion, than in the 
filamentose species and the stamens relatively longer, (Pl. 
35, Fig. 1), so that there is more likelihood of the pollen 
falling on the papillose apex of the stigma or being brought 
near it by conniving petals. In this connection I also 
introduce a figure to show certain variations and deformi- 
ties which sometimes occur in the pistil of Y. filamentosa 
