4 
POPULAR SCIENCE REVIEW. 
are specially adapted (“ purposed ”) to prevent self-fertilisation. 
This I am convinced is an erroneous assumption. 
Researches into the structure of flowers have led me to draw 
the following conclusions : — * 
1. The majority of flowering plants can, and probably do, 
fertilise themselves . Independently of arriving at this conclu- 
sion from a study of nature, I infer it from Mr. Darwin’s results ; 
for he protected a number of plants from insects, and gives two 
lists of forty-nine species in each, the one of plants more or less 
self-fertile, and the other self-sterile without insect aid ; but he 
adds : — “ I do not, however, believe that if all known plants 
were tried in the same manner, half would be found to be sterile 
within the specified limits.” f 
2. Very few plants are known to be physiologically self- 
sterile when the pollen of a flower is placed on the stigma of 
the same flower. The genus Oncidium is a remarkable instance, 
the pollen of some species having even a poisonous action on 
the stigma. J Linum, as Mr. Darwin has shown, is another 
ease, and he observes of L . perenne that “ its own pollen is as 
powerless on the stigma as so much inorganic dust.”§ 
3. Several plants are known to be morphologically self- 
sterile, in that the pollen cannot, without aid, reach the stigma, 
but is effective on that of the same flower. Species of Lupine 
and Salvia are in this condition. 
4. Self -sterile plants from both the above causes can become 
self-fertile. Various conditions appear capable of bringing this 
about. A lowering of temperature seems to check the vigour 
of the stamens in a normally proterandrous flower, and by not 
affecting the pistil equally, the essential organs now mature 
together. Thus Eschscholtzia, which is self-sterile in Brazil, 
became, with Mr. Darwin, self-fertile in England. The mere 
withering of the corolla will often secure self-fertilisation, as in 
the case of pansies (see Plate I., fig. 12) by pressing the 
anthers or pollen on to the stigmas. The closing of the corolla 
in the evening may do the same, as with Buttercups, Anagallis, 
Convolvulus, and other of the Gumopetalae, in which the 
stamens, being adherent to the corolla, the latter, when well 
expanded in sunlight, causes the stamens to spread away from 
the pistil, and in this condition the flowers are ready to receive 
the visits of insects ; but by closing, the corolla carries the 
stamens back again, and so self-fertilisation may be secured. 
* Space will only allow me to give but little more than an enumeration, 
but the reader is referred to my paper (loc. cit.), where each of these con- 
clusions is dealt with in extenso. 
t Loc. cit. p. 370. 
t “ Animals and Plants under Domestication,” ii., p. 135. 
§ “ Forms of Flowers,” p. 98. 
