74 MR. DARWIN ON THE EXISTENCE OF TWO FORMS 
coloured and twisted, were straight and fresh-coloured; and only 
one grain had emitted quite a short tube, which could be drawn 
out of the stigmatic tissue without being ruptured. 
The following experiments are more striking :— 
Sixthly. Y placed own-form pollen on three of the stigmas of a 
long-styled flower, and pollen from a short-styled flower on the 
other two stigmas. After 22 hours these two stigmas were dis- 
coloured, and slightly twisted, and penetrated by the tubes of — 
numerous pollen-grains: the other three stigmas, covered with 
their own-form pollen, were fresh, and all the pollen-grains were 
loose ; but I did not dissect the whole stigma rigorously. 
Seventhly. Experiment repeated in the same manner, with the 
same result. 
Eighthly. Experiment repeated, but the stigmas were carefully 
examined after an interval of only 51 hours. The two stigmas with 
pollen from a short-styled flower were penetrated by innumerable 
tubes; but these were as yet short, and the stigmas themselves 
were not at all discoloured. The three stigmas covered with their 
own-form pollen were not penetrated by a single pollen-tube. 
Ninthly. Put pollen of short-styled on one stigma, and own- 
form pollen on the other four stigmas ; after 24 hours, found the one 
stigma somewhat discoloured, and twisted, and penetrated by many 
long tubes : the other four stigmas were quite straight and fresh ; 
but on dissecting their whole lengths I found that three pollen- 
grains had protruded quite short tubes into the tissue. 
Tenthly. Repeated the experiment, with the same result after 24 
hours, excepting that only two own-form grains had penetrated the 
stigmatic tissue with their tubes, to a very short depth: the one 
stigma, which was deeply penetrated by a multitude of tubes from, 
the short-styled pollen, presented a conspicuous difference in com- 
parison with the other four straight and bright pink stigmas, in 
being much curled, half-shrivelled, and discoloured. 
I could add a few other experiments; but those now given amply 
suffice to show that the pollen-grains of a short-styled flower placed 
on the stigmas of a long-styled flower emit a multitude of tubes 
after an interval of from five to six hours, and penetrate the tissue 
ultimately to a great depth, and that after twenty-four hours the 
stigmas thus penetrated change colour, become twisted, and appear 
half-withered. On the other hand, the pollen-grains of the long- 
styled flowers placed on their own stigmas, after an interval of a 
day, or even three days, do not emit their tubes, or at most only 
three or four grains out of a multitude emit their tubes ; and these 
