ae BOTANICAL GAZETTE [yxy 
show a tendency at least for the pods on the same stalk to produce 
about the same number of seeds, although the number of pods per 
stalk is apparently not a factor. The highest number of seeds taken 
from a single pod was 448 from a pod of plant 4, which bore 4 pods. 
The lowest number, on the other hand (168), was from a pod of plant 
11, with 6 pods. 













TABLE III 
Seeds in Perfect Imperfect Seeds Actual loss 
pod seeds seeds -eaten in per cent 
PM oc ec cs 168 - 12 fo) ° 
Mara: ee cS: 448 245 210 187 64 
BVOIMIES Seis os 280 118 104 5 a 
Baa ee P| 
TABLE IV 
Number of Seeds eaten per Per cent of seeds 
larvae larva eaten per larva 
ee ee 
MONO ic I ° 2 
PeBEIMULE Ou nis ck 12 IOI 32 
WR Se 2.66 19 7 




3- Relation of larvae to seed production 
The most interesting point in connection with the seed pro- 
duction of Yucca is the presence of the larva of the Pronuba moth, 
whose existence depends upon the destruction of some of the seeds. 
Theoretically, a single larva to each pod would give the optimum 
condition for Yucca, as this would represent a single pollination 
by a parent Pronuba. If the number of larvae be greater than 
one per pod, the advantage is on the side of the Pronuba until 
the number of larvae is such that the entire mass of seed produced 
s reeds This last condition would of course exterminate the 
mo 
That one larva to each pod is the optimum number is shown by 
the fact tha 
U9 of the 11 pods in which but a single larva was found 
produced the average number of perfect seeds or more. 
The averages also show that Yucca is successful in seed pro- 
nag even against odds. The average number of larvae per pod 
ound was 3, and of the 26 pods with 3 or fewer larvae 12 produced 
