The Structure and Morphology of the ‘ Ovule/ 
An Historical Sketch. 
BY 
W . C. WORSDELL. 
With twenty-seven Figures in the Text. 
Introduction. 
HE great aspect of botanical science known to us as Morphology 
A comprises that department of study which is concerned with the 
form and the differential characters of the various structures or organs 
composing the individual plant. As this study advanced in the past it 
became clear that all the various parts or organs of the higher plants are 
capable of being grouped or classified into a few main categories, the 
raison d'etre for the existence of these latter being that the organs con- 
stituting each, although exhibiting an extensive range of variation in 
accordance with the equally varied environmental conditions to which they 
inevitably become subjected, yet possess certain well-defined, exclusive 
characters of form, structure, and position which have rendered them during 
the course of ages of progressive differentiation so stereotyped and fixed 
as to preclude the possibility of the existence of any intermediate or tran- 
sitional forms between any two of these categories. It is true that in 
some cases it is excessively difficult, perhaps even impossible, to determine 
the morphological category to which a given organ or structure pertains, 
and this owing to the extreme modification of the latter, resulting from 
certain special adaptive requirements, e.g. the submerged bladder-bearing 
portion of the Utricularia - plant and the seminiferous scale of the Abietineae. 
But this, it seems to the writer, is due solely to our ignorance and in- 
capability of tracing all the stages of adaptive modification which, during 
its long phylogenetic history, the organ in question has undergone, the 
original and all the intermediate forms having long since become extinct ; 
the ontogeny, or individual development, may yield us no clue ; for in 
the majority of these cases the highly modified organ arises congenitally 
as such. If we are unable to discover, say, in the submerged organ of 
U tricularia a prevalence either of the distinctive characters of the pbyllome 
[Annals of Botany, Vol. XVIII, No. LXIX. January, 1904.] 
