270 DR. J. \V. HESLOP HARRISON ON 



pollination in the roses, I was compelled to study the matter 

 in the field, when some very interesting and illuminating 

 evidence was secured. Very early indeed I discovered that, 

 to say the least, pollination in J^osa was conducted under 

 peculiar circumstances. Every morning at 7 a.m. practically 

 every young flower, no matter what its species, provided that its 

 stigmas were mature enough to receive pollen, was already 

 pollinated, and this maturity, since the roses are homogamous, 

 was almost always shown at that hour. Thus it appeared 

 almost certain that, if pollination was effected by insects, it 

 could only be through the action of Noctuidae flying at dusk 

 and dawn, or through Diptera and Hymenoptera busying 

 themselves at daybreak. To determine which was responsible 

 I paid special attention an hour or so after sunset to the 

 blossoms of the day, and to those just ready to burst. At that 

 time, as if by magic, every flower young and old was folded 

 up for the night. Unless then brought about by casual day- 

 fliers like the Noctuids of the genus Miana the agency of 

 moths must be ruled out. There remained then the operations 

 of Diptera and Hymenoptera to be considered. I therefore 

 got up earlier, at 4 a.m. (G.M.T.), before any insects were at 

 work, when I found that even then every newly, expanded 

 R. pinipiiiellifolia had its stigmas powdered with pollen from its 

 own overarching stamens. At the same time those oi R. mollis, 

 R. omissa and R. Lintoni were quite untouched. A little later 

 even their anthers dehisced, after which, unless insect guests 

 performed the necessary operation, on the maturing of the 

 innermost stamen whorls they curved over and deposited 

 their precious dust. In many cases indeed even this curving 

 motion as a mode of self-pollination proved superfluous, for 

 almost without exception, as the flowers mature, several 

 stamens are locked between the stigma heads so that their 

 pollen, as it is shed, of necessity falls on the adjacent stigmas. 

 By one method or another, therefore, in default of outside 

 agencies, self-pollination is automatic. 



Independent of this definite mechanism for utilising their 

 own pollen, the same effect is frequently brought about in 



