FERNS AND FERN ALLIES. 
93 
There are six known species of the genus, three only growing 
in America. O. regalis is almost cosmopolitan, being found in 
America, Europe aud Asia and Southern Africa. O. Claytoni- 
ana occurs in America and India; O. cinnamomea in America 
only. 
As noted in the previous article this genus occupies a par¬ 
ticularly interesting position in the evolutionary scheme of ferns, 
standing as a connecting link between those ancient forms 
which initiate the process of reproduction in hypodermal cells 
and those more modern forms which initiate the same process 
in epidermal cells. The former are technically termed “ eu- 
sporangiate,” the later “ leptosporangiate ” ferns. 
But it is in the study of Clayton’s fern that one of the most 
marvellous series of observations on record even in this day of 
scientific marvels has recently been accomplished. Certain con¬ 
formations of the reproductive organs in the genus Osmunda 
make the plants exceptionably favorable subjects in which to 
observe with the microscope the reproductive processes. They 
were accordingly chosen by Prof. Douglass L. Campbell of 
Leland Stanford University, for special microscopic study, as 
likely to aid him in his critical studies of the mosses and ferns. 
He was in the end rewarded by seeing what the eye of mortal 
man had rarely seen before, had never seen in this class of 
plants, the whole process of fertilization and the growth of the 
new individual from a single primal cell ! (For the particulars 
of this observation see Campbell’s “ Mosses and Ferns,” p. 347.) 
The illustrations furnished for this paper represent a simple 
leaf, Figure 1 ; a pinnatifid leaf, Figure 2 ; a pinnate leaf, 
Figure 3, in which s is the stipe, r the rachis, and p the pinna; 
the bipinnatifid leaf of Osmunda Claytoniana, Figure 4, in 
which s is the segment ; and the bipinnate leaf of Osmunda 
regalis, Figure 5, in which p is the pinnule. It will be observed 
that the pinnae and pinnules in Fig. 3 and Fig. 5 correspond 
to the simple leaf in Fig. 1. The pinnae in Fig. 4 correspond 
to the pinnatifid leaf in Fig. 2, and those of Fig. 5 to the 
pinnate leaf in Fig. 3. 
