Heterospory in Sphenophyllum Dawsoni. 91 
NOTES FROM THE CAMBRIDGE BOTANY SCHOOL. 
I 11 the first number of the New Phytologist 1 a short account 
was given of the method adopted in the practical work connected 
with advanced courses of lectures on Pteridophytes, Gymno- 
sperms and Plant-Anatomy in the Cambridge Laboratory. We 
occasionally notice morphological features in plants under exami¬ 
nation which do not appear to have been previously recorded, and 
it occurred to me to ask the Editor of this Journal to allow us to 
send brief notes on such points as seem to us of sufficient interest 
to publish. 
A. C. SEWARD. 
1 Vol. I., No. 1, 1902, p. 14. 
I.—ON A SUGGESTION OF HETEROSPORY IN 
SPHENOPHYLLUM DAWSONI. 
By D. Thoday, B.A. 
(Scholar of Trinity College, Cambridge). 
[With Text-Fig. 14.] 
It is generally agreed that heterospory has arisen independently 
in several different groups of Vascular Cryptogams. In some of 
these groups the differentiation has proceeded much further than in 
others; in some its beginnings are suggested. Among fossil plants 
Calamostcichys is interesting in this connexion, since one species, 
C. Caslieana, is distinctly heterosporous, although the megaspores 
are only three times as large as the microspores; while C. Binneyana 
is isosporous; but abortive spores have been figured by Williamson 
and Scott, 1 the survivors attaining a size slightly above the normal. 
Abortive spores are found also in the megasporangia of C. Caslieana. 
Up to the present nothing of this kind has been recorded for 
Sphenophyllum. Renault’s opinion that one of his French specimens 
showed heterospory is considered by Zeiller 2 and by Williamson 
and Scott to be based on a misinterpretation, and it is now generally 
agreed that Sphenophyllum is homosporous. As will be seen from 
the figure, the present observation shows that something of the 
1 Williamson and Scott, Phil. Trans. R. Soc., Vol. 185B, 1894, 
p. 911. 
Zeiller, Mem, Soc- Geol, France, 1893, 
