70 Worsdell . — The Structure and Morphology of the ‘ Ovule l 
2 . That the pollen-sac and nucellus are identical as to their mode 
of development, which is here a proof of true homology, confirmed besides 
by a comparative study of these organs in the whole vegetable kingdom 
and by a series of teratological cases. 
3. That the pollen-sac, like the sporangium (the common fundamental 
form of pollen-sac and nucellus), is everywhere attached to a leaf; con- 
formably with this truth we are assured, in a totally different manner, 
that the ovule-rudiment is, in fact, of foliar nature. 
This last view is supported by the study of Cycads. And he further 
says that we have seen that these metablastemata are everywhere attached 
to phyllomes and not to caulomes. As regards the true position of the 
nucellus, he says that in a general way it is to be regarded as terminal 
to the ovular rudiment. On the other hand, the teratological cases show 
it to be lateral an d appear to indicate the true, or at least the primitive, 
relations existing between the two organs. 
At the end of Chapter III he says : ‘ It seems proved that the integument 
of Angiosperms is a special structure pertaining to the ovular leaflet and 
of foliar nature.’ This author’s treatise must be regarded, from its 
thoroughness of detailed investigation and breadth of treatment, as one 
of the most weighty contributions to this great and difficult subject, and 
of great interest in demonstrating how far developmental data serve in 
fixing the morphological dignity of the ovule. 
Celakovsky (38) stands out as a very brilliant exponent of the 
foliolar theory of the ovule, his contributions to the subject being, in the 
writer’s opinion, remarkable for their deep insight into, and ingenious 
handling of, one of the most difficult problems in botanical science. As 
the writer is also inclined to believe that in the sum of the numerous 
treatises of this author on the subject is contained a probable solution 
of the great problem as to the real morphological nature of the ovule, 
more space will be allotted to the consideration of his views than has been 
the case with the other authors cited above. 
Firstly, with regard to the various methods employed in determining 
the morphological nature of any doubtful structure, these may be said to 
be four in number, and may be termed : (a) the developmental, ( h ) the 
comparative, {c) the anatomical, (d) the teratological. Applying these 
methods in turn to the solution of the nature of the ovule, it will be seen, 
in the first place, that the study of the development or ontogeny of this 
organ tells us simply that it is a protuberance borne sometimes on an axis, 
sometimes on a foliar organ, producing in basipetal order two lateral, cup- 
shaped appendages. Relying entirely on the ontogenetic facts and assuming 
that the ovule is a bud would surely be dangerous ; for we cannot be sure 
that it is not an organ of a totally different nature, arising from the earliest 
stage of development, as a congenitally-modified structure. Of this latter 
