58 Campbell. — On the Prothallium and Embryo of 
namomea , otherwise perfectly normal (Fig. 31). They were 
thin irregular plates, many times larger than the normal ones, 
in some cases so large as to cover completely one side of the 
cell. Whether these were the result of simple arrest in the 
normal division, due to some unexplained reason, or, as is less 
probable, were reversions to an earlier type, such as Anthoceros , 
where there is normally but one chloroplast in a cell, it is im- 
possible to say. 
Goebel 1 states that unfertilized prothallia of O. regalis may 
live for several years and reach a length of 4 cm. In my 
cultures of O. cinnamomea and O. claytoniana , the prothallia 
were still growing vigorously more than a year after the 
spores were sown, and probably would have continued to do 
so had they been preserved. 
Goebel 2 also describes a dichotomy of the older prothallia 
of O. regalis , but I failed to find any cases among the pro- 
thallia of the species examined by me ; but it is not at all 
unlikely that it may occur. The formation of lobes close to 
the growing point, which is very common in O. cinnamomea , 
may possibly be a case of suppressed dichotomy, as in an 
undetermined species of Polypodiaceae examined by me, in 
which a true dichotomy occurred, this was brought about by 
the central part of the apical region growing out into a lobe 
dividing the growing point into two as in various liverworts. 
The formation of these lobes in the Osmundaceae gives the 
older prothallia their peculiar wavy outline. (See Goebel, 
Outlines, p. 199. Fig. 148.) 
The Antheridium. 
Under favourable circumstances the antheridia appear in 
O. claytoniana a little more than a month from the time of 
germination, and continue to form for at least a year. How 
much longer they might continue to develop I cannot say. In 
O. cinnamomea the first antheridia appeared about two weeks 
1 Goebel, Outlines of Morphology and Classification, p. 199. 
2 L. c. p. 200. 
