(1922) 
Inversely, the pollen of Pentas germinates on the stigma of Impa- 
tiens sultant. 
Finally I wish to observe that the 3 mentioned species of Impa- 
tiens can form germinal tubes on one another’s stigmas. 
Returning to Torenia and Mimulus we have to pause a moment 
at the question what use those plants can draw from the possession 
of an irritable stigma. This question should be considered regardless 
of the advantage which many plants, — albeit not all!), — can 
have in possessing a stigmatic fluid of such a composition that not 
each kind of pollen can develop in it. 
That advantage the plants would likewise enjoy if their stigmas 
had not the power of shutting. 
It is the general opinion that the movements of the stigmatic 
lobes of Mimulus will prevent the self-fecundation of the flowers. 
It is i. a asserted by BATALIN®), that when a bee without pollen 
on its back penetrates a flower, it touches the stigma and when 
then the bee laden with pollen flies away, it cannot rub off the pollen 
on the stigma of the same flower. When entering another flower, 
however, the pollen is brushed off on the stigma, by which cross- 
fertilisation is effected. I doubt, however, whether the insect can 
actually contribute to the fecundation of Mimulus by pollen of 
another individual. 
Mimulus being a profusely flowering plant, the other flower referred 
to: the one visited after the first, is all but always a flower of the 
same plant. That flower gets pollen from the first, the third from 
the second, the fourth from the third, and so on. Finally the bee, 
still laden with pollen of Mimulus, leaves the plant and may carry 
this pollen to the first flower of another Mimulus; but the chance 
that it will directly return again to a Mimulus does not appear 
greater to me than its visiting quite another plant. 
But let this be as it may, albeit that the structure of the flowers 
of Mimulus has given rise to the opinion that the irritable stigmas 
prevent self-fertilisation, because first the stigma is touched before 
the insect comes in contact with the anthers, this holds only good 
1) From STRASBURGER’s experiments may be inferred that often germination of foreign 
pollen on the stigma and the entering of foreign pollen-tubes into the style-canal and 
the ovarium do not prevent the development and growth of the plant’s own pollen- 
tubes and the normal course of the fertilisation. 
*) A. BararIN. Beobachtungen ueber die Bestäubung einiger Pflanzen. Bot. Zeit 
1870. p. 53. 
