SEXUALITY IN PLANTS. 
365 
female, as happens not unfrequently in some buttercups, lesser 
celandine {Ranunculus)^ and others. 
Conversely, if the pistil be not developed the adult flower 
will be male, as happens in many Umbellifers and Caroyphyllese. 
The exact opposite of this change occurs when flowers usually 
of one sex become bisexual by the development of stamens or 
of pistils, as the case may be. Instances of this kind are com- 
mon in almost all normally unisexual flowers. If the uni- 
sexual condition of an ordinary bisexual plant be considered 
from a structural point of view as an arrest of development, the 
present instance must be attributed to an exaltation of that 
process. 
There is another way in which an ordinarily one-sexed flower 
may become two-sexed, and that is by the more or less perfect 
change of stamens into pistils, or of pistils into stamens. 
This is sometimes the result of a substitution of one part for 
another, but in other cases of an actual permutation. A 
stamen becomes converted at a certain stage of its growth into 
a pistil, or vice versa. Such changes are by no means uncom- 
mon in plants. We may thus have a stamen assuming the 
guise of a pistil, a pistil endowed with all the attributes of a 
stamen ; we may even have pollen formed within the tissues 
of the ovule itself, as has been seen in a passion-flower and in a 
rose. A more complete hermaphroditism can hardly be con- 
ceived. 
So far we have been dealing with individual flowers, but 
analogous changes occur throughout the whole organism. Thus 
many plants, under ordinary circumstances, produce unisexual 
flowers, male and female, on the same individual. Such are the 
plants called monoecious, Now it sometimes happens that 
plants of this character become entirely unisexual by the 
development of male or of female flowers, only to the exclusion 
of the other. Such occurrences are not uncommon in mulberries 
and walnuts. 
The converse of this is, when a plant ordinarily producing 
flowers of different sexes on different individuals {dioecious) 
forms flowers of both sexes on the same plant, becomes, in 
other words, monoecious. This occurs occasionally in the hop. 
These changes in the structural condition of the flower, va- 
riously modified and combined in diflerent cases, constitute all 
the changes in the sexual organisation of the flower which 
concern us at present. May we not say of these puzzling 
transformations what Horace said of a girlish-looking youth — 
Mire sagaces falleret hospites 
Discrimen obscurum, solutis 
Crinibus ambiguoque vultu. 
