YUCCA MOTH AND YUCCA POLLINATION. lil 
arduous work; but it is probable that, seeing that this 
liquid is not nectarian, Professor Trelease is right in 
stating that the tongue is used to thrust the pollen further 
into the cavity than her tentacles can reach, though I 
can see no necessity for this action so far as pollination is 
concerned. After the more vigorous motions of thrusting 
the pollen into the tube, she frequently rests in comparative 
quiet, working her tongue in the tube sometimes for four 
or five minutes together, but ordinarily the act of pollina- 
tion ceases with the few vigorous thrusts already described. 
The importance of this act will be better appreciated when 
I state that numerous experiments in artificial or brush 
pollination have shown that effective fertilization in Yucca 
jilamentosa is by no means an easy matter, and that it 
rarely takes place as effectively as through the actions of 
Pronuba. 
This carrying of the pollen to the stigma generally fol- 
lows every act of oviposition, so that where ten or a dozen 
eggs are consigned to a single pistil, the stigma will be so 
many times be-pollened. The ends of the tentacles, which 
are most setose and spiny, and which are always curled 
into the pollen mass when not uncoiled, must necessarily 
carry anumber of pollen grains into the stigmatic tube 
each time pollination takes place; and I have noticed a 
gradual diminution in the size of the collected mass, corre- 
sponding to the work performed, which is indicated by the 
rubbed and worn appearance of the individual, the freshest 
specimens always having the largest loads. I have also 
noticed that where oviposition occurs thrice in the same 
pistil (and this is most common), the three corresponding 
acts of pollination are consecutively in the three deeper 
notches of the style, thus insuring a supply for the ovules 
in each carpel. Pollen collecting is, however, sometimes 
continued after oviposition has begun, but is rarely witnessed 
during the active period of egg-laying. This is, however, 
invariably followed by pollination, though not always alter- 
nating therewith. Indeed it is not uncommon for a female 
