330 HETEROMORPHY. 
dimensions as another; one flower resembles very closely 
another flower of the sameage andsoon. Nevertheless 
it occasionally happens that there is a very considerable 
difference in form in the same organs, not only at 
different times, but it may also be at the same time. 
Descriptive botanists recognise this occurrence in the 
case of leaves, and apply the epithet heterophyllous to 
plants possessed of these variable foliar characters. 
In the case of the flower, where similar diversity of 
form occasionally exists, the term dimorphism is used. 
As these phenomena appear constantly in particular 
plants, they are hardly to be looked on, under such 
circumstances, as abnormal, but where they occur in 
plants not usually polymorphic, they may be considered 
as coming within the scope of teratology. 
Heterophylly——As a general rule, the leaves or leaf- 
organs in each portion of a plant, from the rhizome or 
underground axis, where it exists, to the carpellary 
leaf, have their own special configuration, subject only 
to slight variations, dependent upon age, conditions of 
growth, &c. The cotyledons are very uniform in 
shape in each plant, and are scarcely ever subject to 
variation. ‘The leaves near the base of the stem, the 
root-leaves as they are not unfrequently called, some- 
times differ in form from the stem-leaves; these again 
differ from the bracts or leaves in proximity to the 
flower. The floral envelopes themselves, as well as 
the bud-scales, all have their own allotted form 
in particular plants, a form by which they may, in 
most cases, be readily recognised. Hence, then, in 
the majority of plants there is naturally very consider- 
able difference in the form of the leaf-organs, accord- 
ing to the place they occupy and the functions they 
have to fulfil; but, in addition to this, it not unfre- 
quently happens that the leaf-organs in the same por- 
tion of the stem are subject to great variation in form. 
This is the condition to which the term heterophylly 
properly apples. The variation in form is usually 
