618 OCCASIONAL NOTES OS PLANTS, 



both stamens and pistils are found in the same flower, does not 

 prove either one theory or the other. Dr. Asa Grraj, Professor 

 of Botany of the Harvard University, in the last edition of his 

 •work on " Structural Botany," says,* " Separation of the sexes 

 (in plants) is a direct adaptation to intercrossing, rendering it 

 necessary in dioecious, and largely favouring it in most monoecious 

 and polygamous flowers. Strictly close, or self-fertilization can 

 occur in hermaphrodite flowers only ; but it is in these very plants 

 that the most curious adaptations for intercrossing are revealed." 

 Then, after referring to a particular case, he says, " cases like 

 this, and hundreds more, all equally remarkable, serve to show 

 how sedulous, sure, and economical are the adaptations and 

 processes of Xature for the intercrossing of hermaphrodite 

 flowers." 



Bnt even if the stigma should be found in a moist state, and 

 covered with pollen from the anthers of its own flower ; that is no 

 proof that self-fertilization has or will take place. In some 

 instances the anthers closely envelope the stigma, the cells open- 

 ing on the inside and shedding their pollen directly upon it ; but 

 the stigma rises through them carrying the pollen with it, high 

 above the rest of the flower ; not to utilise for itself, but to 

 present it to the visits of insects or to the action of the wind ; 

 either of which, or both, soon carry it away and thus disseminate 

 it for the fertilization of other plants. That stigma, however, is 

 then free to receive in its turn, the pollen of other flowers, when 

 it shall have itself matured. If such a stigma, when it first rises 

 above the anthers, is cleared of the pollen by a camel hair pencil 

 it will be found (if moist at all) to be moist from dew or some 

 other cause ; not from the viscid secretion from its own substance- 

 proper to it when it is mature ; and a moderately high micro- 

 scopic power will exhibit its surface (when it is not clothed with 

 hairs as is often the case) smooth and horny ; not spongy as it 



* " Structural Botany," Asa Gray, 1880, pp. 217 and 223. 



