142 Shaw—Structure of the Flowers in 
tion for any reason took place before the flower opened, the 
corolla would cease developing. ‘‘I believe that cleistogamy 
is caused by the physiological condition of great fertility 
without crossing, coexisting with the morphological one, of 
germination of the pollen while on the anther cell, or at least 
before expansion of the perianth. The result of the latter 
condition is the arrest of the floral envelopes.”’ 
Since cleistogamic flowers are often buried in the earth, and 
so produce fruits which are safe from the danger of being 
nipped by herbivorous animals, the question of cleistogamy 
has been identified with that of specially protected forms of 
fruit. Huth,! speaking particularly of the case of Polygala 
polygama, says: ‘‘One must look upon this case also as a 
contrivance for protection against grazing animals.” The 
force of this explanation disappears when one takes into account 
the aérial cleistogamic flowers. Polygala polygama grows 
largely where tender grasses are not abundant, and suffers 
much from grazing animals. The green cleistogamic flowers, 
growing among the foliage, are situated as unfavorably as 
possible to escape these, and therefore Huth’s statement 
obviously fails to explain them. If any one chooses, he can 
assume that the two kinds of minute flowers have two differ- 
ent explanations, that the subterranean ones are developed to 
produce protected seeds, and the aérial ones for another pur- 
pose. But if one believes, as does the writer, that one expla- 
nation should chiefly cover the whole case ina single plant, 
the idea of these flowers being developed for the sake of pro- 
tection must be dropped, except as a secondary condition. 
Chodat,” also writing of Polygala polygama in particular 
speaks of it as a case of teratology, and differing from other 
abnormalities only in the frequency of its occurrence. Is it 
not difficult to suppose, either that this plant is essentially 
1 Loc. ctt. 
2 Toc. cit. 
