238 MOSSES AND FERNS chap. 



projecting at all above the surface of the prothallium, and 

 closely resembling in form the archegonium of the Marattiacese. 

 Each of the four rows of neck cells contains three or four cells. 

 The basal cell may undergo divisions, but its limits remain 

 clearly visible in the ripe archegonium. 



According to Mettenius ((2) PL xxx, Figs. 18, 19), O. 

 pedunculosum differs from O. pendulum in having the outer 

 wall of the antheridium double, as it is in Botrychimn. The 

 neck of the archegonium is also somewhat longer than in 

 O. pendulum. Bruchmann's account of O. vulgatiim agrees 

 closely with that of Lang for 0. pendidum. 



Botrychium 



In July, 1903, the writer found at Grosse Isle, Michigan, a 

 number of old prothallia of Botrychium Virginianum, with the 

 young sporophytes still attached, but nevertheless showing the 

 older stages of the sexual organs. In 1896, Jeffrey (i) was 

 fortunate enough to secure abundant material of this species, 

 including young prothallia, and succeeded in tracing very com- 

 pletely the development of the reproductive organs and embryo. 

 Owing to the kindness of Professor Jeffrey, who sent preserved 

 material, as well as prepared slides, I have been able to confirm 

 the results of his investigations. 



The prothallium (Figs. 126, 127) is a subterranean, tuber- 

 ous body, much like that of B. lunaria described by Hofmeister, 

 but is very much larger. The specimens collected by the writer 

 were buried several centimetres below the surface, in rather dry 

 woods ; Jeffrey's material was in part found in a sphagnum bog, 

 partly in dryer localities. 



The 3^oungest specimens found by Jeffrey were oval, slightly 

 flattened bodies, which bore only antheridia. These occupied 

 the middle line of the upper surface, which later develops a 

 median ridge upon which the antheridia are borne, while arche- 

 gonia appear later on either side of the antheridial ridge. ( Fig. 

 126, B). In B. lunaria, according to Hofmeister ((i), p. 

 308), the archegonia are mostly formed upon the ventral 

 surface. ; 



A section of the prothallium shows that the superficial tis- 

 sues are composed of relatively transparent cells, while the inner 

 tissue, especially toward the ventral side of the thallus, has very 

 dense contents, there being an oily substance present, as well as 



