181 



in the absence of light develops a dorsi- ventral prothallium. 

 Some recent experiments of Peirce (Studies of Irritability 

 in Plants, Ann. of Bot., LXXX : 449, lOOfy) upon Anthoceros 

 and certain liverworts may be interesting in this connection. 

 While in Fimhriaria calif arnica and the prothallium of Gpnno- 

 gvamme triamjitlaris equal exposure to light on a klinostat could 

 not destroy the tendency to bilateral development, in Anthoceros 

 it was quite annhilated by this equal illumination. Biiuchmann 

 states that the prothallium of 0. vuhjaiuni will develop chloro- 

 phyll under the influence of light, but will not become flattened. 

 The writer has kept prothallia of 0. penduhun exposed to the 

 light for more than two months without any evidence of 

 chlorophyll being developed, nor is there any change in the 

 form, although the growth continues slowl}'', and apparently in 

 a perfectly healthy way. 



Assuming that (A moluccanum would behave much as 0.j)edun- 

 culoswn, which it otherwise so closely resembles, we may assume 

 that it represents the most primitive of the three types — 

 0. moluccanum, 0. vulgatum and 0. pendulum. The occasional 

 slight development of chlorophyll in the germinating spores 

 and the power to develop chlorophyll later under exposure to 

 light point to this type being nearest the green gametophyte 

 from which presumably these colorless saprophytic forms 

 have arisen. 



The rapidity of spore germination and the delicacy and small 

 size of the older gametophyte, as we have already pointed out, 

 indicates that in (J. moluccanum, the gametophyte is an annual 

 strncture. This is probably also the case with Helminthostachys. 

 Many prothallia of the latter, with the young sporophyte 

 attached, were collected by the writer in Ceylon, but all 

 were practically of the same age. They were growing in a 

 forest which was periodically snbu erged, and it looked as if 

 in this plant, as in 0. moluccanum, complete submersion in 

 water was a necessary condition for germination. The hot, 

 humid climate where both forms flourish would naturally induce 

 a rapid growth, and it is hardly likely that the small pro- 



