912 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
In C. Casheana, the same process, carried further in certain sporangia, has led to 
the formation of specially favoured macrospores, to which, as we may presume, the 
production of a female prothallus was entrusted. Even in C. Casheana, however, 
the heterospory is not so extreme as in some other Cryptogams, for numerous macro- 
spores are still developed in each sporangium, and their diameter is only about three 
times that of the microspores. 
We suggest then, that in Calamostachys we have a genus in which the first rise of 
the phenomenon of heterospory can be traced. That the same phenomenon arose 
independently in various groups of vascular Cryptogams, has long been recognized. 
We have found no evidence in C. Binneyana for the existence of a cellular body 
within the spore, such as M. Renavtt believes to be present in the spores of this and 
other species. One of us (D. H. Scort) has had the advantage, through the kindness 
of M. Renavtt, of seeing some of the preparations in question, but was not convinced 
that the structure within the spore was really cellular. 
Compared, for example, with the cellular mass in the pollen-grain of Cordaites, as 
shown in M. Renavtr’s classical preparations, the appearances in the Calamostachys 
spores appeared very doubtful. In our own specimens, the endosporium has usually 
contracted away from the exosporium. When the endosporium and its contents are 
much shrivelled, an appearance resembling a cellular structure is sometimes produced, 
but such appearances are quite inconstant, and are, we believe, illusory. 
In the mature spores of Calamostachys Binneyana we often observe three radiating 
cracks at one pole, such as are so frequently seen in the spore-membranes of recent 
Cryptogams. Between these cracks three well-defined brown masses can usually be 
detected. In sectional views of the spore we find that these bodies are attached to 
the inner surface of the spore-membrane (see Plate 81, fig. 33a; Plate 82, fig. 34, D). 
Other specimens proved that the attachment is to the exosporium. We regard these 
masses as local thickenings of the cell-wall, not by any means as distinct cells. 
Before discussing further the affinities of Calamostachys Binneyana, it will be 
necessary to take into consideration the structure of the other forms which we bave 
examined. 
CALAMOSTACHYS CASHEANA, WILL. 
The heterosporous form of Calamostachys was originally described in 1880* from a 
specimen found at Halifax. In this specimen three whorls of sporangia are shown 
in the obliquely tangential section. The uppermost whorl shows microsporangia 
only ; in the lowest, only macrosporangia are found, while the intermediate whorl 
contains both kinds intermixed. 
The geuveral habit of the specimen is very similar to that of C. Binneyana, with 
* Wittiamson, “ Organization,” Part IL, p. 298; Plate 54, fig. 24 (O.N. 1024 and 1025). M. Renavrt 
has also established the existence of heterospory in Annularia longifolia, Bronen. ‘Ann. Sci. Nat., 
Bot.,’ sér. 5, vol. 18, 1873. (Also in ‘Cours de Botanique Fossile,’ vol. 2, 1882, p. 126.) 
