IOT 
Sphen ophyllales . 
manites Romeri there has been, accompanying the sterilization of 
the dorsal lobes, a fission of the ventral sporangiophores ; this is 
borne out by the fact that in Bowmanites the sporangiophores are 
twice as numerous as the bracts, and that they bear two and not 
four sporangia. It would seem that in Sphenophyllum Dawsoni 
and the numerous allied cones this fission of the sporangiophore 
was accompanied by the reduction of the sporangia on each half 
(which then came to constitute a sporangiophore) to a single one. 
The origin of the type of S. majus and 5. trichomatosurn cannot be 
explained on this theory until their anatomy is known, but it is 
quite possible that in the former a sterilized dorsal lobe or bract 
subtends a much reduced sporangiophore bearing four sporangia ; in 
this case the structure would be primitive in so far that the bracts 
and sporangiophores are equal in number, and the latter bear four 
(or more) sporangia. This reduction in number of the sporangia 
borne, on a sporangiophore, and the chorisis or fission of the latter, 
have been suggested by Professor Bower (3), but as he does not 
consider the sporangiophores and bracts as ultimately homologous, 
he would not, of course, accept the above interpretation of the 
homologies of the cones of the Sphenophyllales. 
It is still doubtful whether all Sphenophyllales were homo- 
sporous; no undoubted case of heterospory has been discovered, 
though Mr. Thoday found a suggestion of it in Sphenophyllum 
Dawsoni, where there was a slight difference in size between the 
spores in certain sporangia, the larger spored sporangia occurring 
towards the base of the cone, where megasporangia are usually 
found (12). Dr. Scott subsequently expressed the opinion that 
heterospory is unknown in Sphenophyllum, although an appreciable 
difference in the size of the spores has been noted (9). 
LITERATURE QUOTED. 
1. F. O. Bower. “Studies in the Morphology of the Spore-producing 
Members. I.—Equisetineae and Lycopodineae.” 
Philosophical Transactions of the Royal Society of 
London. Series B., Vol. 186, 1893. 
2. ,, II.—“ The Ophioglossacea:.” Dulau & Co., 1896. 
3. ,, V.—“General Comparison and Conclusion.” Philoso¬ 
phical Transactions of the Royal Society of London. 
Series B., Vol. 196, 1903. 
4. 
“ The Origin of a Land Flora.” 1908. 
