174 BOTANICAL GAZETTE [SEPTEMBER 
the spore content. Campbell in his Mosses and Ferns, published in 
1895, gives an account of his investigation of S. Krvaussiana. He 
too describes “the single large globular nucleus’’ (z.e¢., the proto- 
plasmic vesicle) of the megaspore. The diaphragm which exists 
in this species he explains as arising, not as Pfeffer thought from 
the first division of the spore, but from the thickening of the walls 
of the lowermost layer of cells of the disk at the spore apex. He 
finds “numerous small nuclei” scattered through the protoplasm 
of the spore cavity, and the protoplasmic layer thickens until it 
‘completely fills the cavity of the spore.” I have examined 2 
Kraussiana with reference to these points. The diaphragm is 
very evident and obviously formed in the manner described by 
Campbell. I can demonstrate no nuclei at any period in the 
spore cavity, nor any protoplasm. The protoplasm forms a layer 
next the wall, as in S. apus, and the vacuole within is full of food 
matter, at first a fluid, then an emulsion, and finally filled with 
granules and small balls of matter which stain like nuclei. The 
protoplasmic layer grows thicker, but never fully occupies the 
interior space as Campbell describes. 
The latest contribution is that of Fitting (1900), ‘‘ Bau und 
Entwickelungsgeschichte der Makrosporen von Isoétes und 
Selaginella und ihre Bedeutung fur die Kenntnis des Wachstums 
pflanzlicher Zellmembranen.” He corrects the error made by 
each of the above named writers in interpreting the parts of the 
megaspore. An attempt to discover the exact origin of the 
megaspores failed, due to the fact that the spore mother cell 
stained so deeply in all his preparations that the details of the 
evolution of the four spores could not be made out. He was 
unable to avoid shrinkage of cells. There follows a very 
detailed account of the development of the spore coats, in which 
he differs from Heinsen as regards their origin. He drew con- 
clusions largely from living material examined in a salt solution. 
As I have said before, the interpretation of the origin of the 
spore coats seems to me largely a matter of theory, and one 
who has examined the young spores of S. apus, while inclosed 
in the sporangium and surrounded by sterile mother cells, is 
