On a Cone of Calamostachvs binneyana. 257 
from C. binneyana in the size and the form of the parts. The 
present work upholds Dr. Kidston’s view. 
It may be noticed, however, that the differences between 
several of the impression species are apparently not great, and it is 
also just possible that previously, more than one species of petrified 
cone has been included under the name of C. binneyana , In examining 
the specimens of this cone in large collections such as Williamson’s, 
it has been found that many of them differ in slight details, such as 
the shape of the cone and the construction of the bracts. The axis 
also seems to present many variations, but these may be wholly 
dependent on the plane in which the section is cut. Again, apart 
from heterospory the differences between C. binneyana and C. 
casheana, are but slight. Perhaps then, a closer study of the details 
of the cones, and the discovery of more specimens in continuity with 
leaves like the one described here, will show that the designation 
Calamostachys binneyana should be applied rather to a type of 
structure than to a species. In view of this, it seems advisable to 
adopt for my cone a specific name founded on the foliage characters, 
viz., Calamostachys grand is. 
Morphological Considerations. The present specimen is of some 
interest in the discussion of the morphology of the cones of the 
Equisetales. 
Summaries of the various views put forward as to the nature 
of the bracts and sporangiophores have been recently given by 
Professor Bower 1 and Lady Isabel Browne 3 , and need not be repeated. 
Of the four current theories, the latter author adopts the view that 
the bracts of Calamostachys represent sterile lobes of the sporophylls, 
which have assumed their present structure and function by the loss 
of fertility. I am quite unable to support this theory. It has been 
shown above that the bracts are most probably foliar organs, and 
identical in structure, arrangement, and perhaps in number, with the 
leaves, though modified for their protective functions. It seems quite 
unnecessary to look upon them as anything but leaves, and it is 
highly improbable that a sterilized sporophyll lohe should assume 
the exact structure and position of a leaf. 
Though the present work bears on the nature of the bracts 
it throws little new light on the sporangiophores. These may be 
(i.) fertile lobes of the sporophylls, (ii.) cauline or axial structures, 
(iii.) organs sui generis. There are difficulties in each of these 
theories. In the case of the first, the numerical relations of the 
1 Bower (08), pp. 381—384. 2 Lady Isabel Browne (09), pp. 2—21. 
