50 Campbell —On the Prothallium and Embryo of 
in the latter only a few pairs of the middle ones bear spores. 
A study of the histology, especially of the root 1 , shows 
marked differences in the two species, and this is true also of 
the prothallium. 
The spores from which the prothallia here described were 
grown, were sown at intervals from the 3rd to the 27th May, 
1890, and the observations were continued until about the 
1st June, 1891. The spores of O. claytoniana were gathered 
near Bloomington, Indiana, in part, and partly near Green- 
castle, Indiana. In the present year (1891) the spores ripened 
the last week in April, about a week earlier than in 1891. I 
am indebted to Prof. Bastin of Chicago for abundant material 
of O. cinnamomea , gathered near that city about May 27. 
The ripe spores of both species (Fig. 1) resemble each other 
closely. They are nearly globular in form, and the colourless 
exospore sufficiently transparent to show clearly the character 
of the contents. The exospore is covered with numerous 
small protuberances, and on the upper surface are the three 
radiating ridges that show where the spore was in contact with 
the sister-spores in the mother-cell. These ridges are very 
conspicuous, and indicate where the exospore is ruptured when 
the spore germinates. The endospore is thin, though suffi- 
ciently evident, but does not show the cellulose-reaction before 
germination; and it is probable that here, as in Gleichenia * , 
there is a new cellulose membrane formed inside the endospore, 
as the first sign of germination. The large nucleus, containing 
a conspicuous nucleolus, occupies the centre of the spore, but 
is somewhat obscured by the dense mass of chloroplasts that 
surrounds it. Although these are so crowded as to render the 
individual ones indistinct, there is no question that even in the 
ungerminated spore separate chloroplasts exist, and that the 
chlorophyll is not present in an amorphous condition as de- 
scribed by Kny 3 and others. 
1 Campbell, On the apical growth of the roots of Osmunda and Botrychimn ; 
Bot. Gazette, Feb. 1891. 
2 Rauwenhoff, La Generation sexuee des Gleicheniacees; Archives Neerlandaises, 
T. XXI. p. 157-231. 
* Kny, Entwicklung des Vorkeimes von O. regalis ; Pringsh. Jahrb. VIII. p. 8. 
