272 TRANSACTIONS OF THE CANADIAN INSTITL'TE. [VOL. V. 



probability, only one in a year. Attached sporophytes, five or six 

 years old, are sufficiently common, as has been already stated in the 

 preliminary notice.'" 



The prothallia described in the foregoing account were from two 

 to twenty millimetres in length, and from one and a-half to fifteen 

 millimetres in breadth. The gametophyte of B. virginianum is thus 

 considerably larger than any geophilous prothallus which has yet been 

 described. Attempts have been made to germinate the spores of this 

 species, but although these are still undecayed, no signs of growth have 

 yet made their appearance after eighteen months. Professor Douglas 

 Campbell got them to sprout in less time than this, but doubtless the 

 warmer climate of California had some influence in hastening the process. 

 He found a few large chloroplasts in the young plants ; but it seems 

 probable that the presence of chlorophyll here is accidental, and depends 

 on the spores being sown contrary to the natural conditions, in the light- 

 An analogous phenomenon occurs when potato tubers are grown under 

 conditions of illumination. Most of the prothallia collected by the 

 writer were found ten centimetres or more below the surface of the soil. 

 Mature sporophytes have been dug up, with the foot-tubercle still intact, 

 and buried often thirty centimetres in the ground. These facts make it 

 very difficult to imagine that the tubercular, deeply subterranean, 

 gametophyte of B. virginianum can have been preceded by a green 

 aerial phase as are the quite superficial, colorless, gametophytic buds of 

 Vittaria, Trichoinanes and HymenopJiyllinn described by Goebel, or the 

 larger tuberlike, resting phase of the liverwort GeotliaUus recently studied 

 by Campbell. It is perhaps worth while to suggest that the slow 

 germination of the spores in the case of Pteridophyta, with subterranean 

 prothallia is an adaptation to enable the former to reach a favorable 

 depth in the substratum, before beginning their growth. 



V. 



A cross-section of the prothallus, such as is represented in figure 15, 

 reveals a number of important features. The antheridial ridge, x., is 

 seen above, containing several antheridia. On its sloping sides are the 

 archegonia, y. Multicellular hairs are often found attached to the ridge, 

 to its flanks and to the base of the prothallium. The position of several 

 of these is indicated in the figure at h. The internal cells, a., of the 

 upper part of the plant appear light in color, and contain protoplasm 

 and small quantities of starch. The lower cells, h.^ both in fresh and 

 stained sections, are dark-colored, and in their natural condition, filled 



10. Can. Inst. Proceed. Vol. i. Pt. i, p. lo. Annals of Botany. Vol. xi., p. 485. 



