74 BOTANICAL GAZETTE [JULY 
between the areas of seed-producing yuccas and those without seed- 
producing plants, yet the local distribution of the seed-producing 
plants obtained in all cases. 
2. Seed production 
The seed pods as collected in the field were placed in small 
paper bags. In the subsequent counting of the seeds of each pod 
three classes were recognized. Seeds of the first class were termed 
perfect seeds; these were the uniform, well-filled, shiny black seeds 
which were uninjured, that is, they were apparently perfect seeds 
so far as could be determined by inspection. The second class 
included all the seeds injured by the larvae, and they are listed as 
seeds eaten. As the Pronuba larva grows it eats its way up through 
the center of the column of flat seeds, which are stacked vertically 
in the pod like a pile of coins. The seeds which had been eaten were 
usually ring-shaped, as only the central portion was destroyed. 
The diameter of the atea destroyed increased as the top of the 
pod was approached, since the larva grew as it ascended the column 
of seeds. Often seeds taken from the top of the pod were almost 
completely eaten, while those from the bottom were perforated by 
oles r mm. or so in diameter. Asa rule, the injured seeds remained 
in place in the pod and were usually cemented together by the 
excrement of the larva. There was some evidence that the seeds 
omaha to fill out even after the larvae perforated them, as the 
seeds so injured were of about the same thickness as the uninjured 
seeds. The number of white infertile seeds was also apparently 
the same in the columns of injured seeds as in the columns of 
uninjured seeds. In the third group, termed imperfect seeds, were 
placed the infertile white seeds and the few malformed black seeds. 
In separating the seeds of this group and of group one there was 4 
FSi for error; it was often difficult to decide whether a seed was 
of one class or the other. Since most of the good seeds, however; 
i regia this discrepancy is within the probable error. 
summarized | : Individual pods is given in table II, and the 
a oe Sin tables III and IV. The pods from each 
sted Separately, 
The average number of seeds produced was about 300 per pod. 
