624 MOSSES AND FERNS 



Asplenium nidus). From the position of the older gametophytes, it 

 was clear that they had been growing for many years, and Bruchmann 

 (5), in his study of the prothalhum of 0. vulgatiim, found this was 

 also true in that species. 



The spores of O. Moluccanum germinate in a few days, and divide 

 into three or four cells, growing at the expense of the food materials 

 in the spore, which is destitute of chlorophyll. Faint traces of chloro- 

 phyll were noted in a few cases, but after exhausting the food matter 

 in the spore, the young gametophyte, in all cases, finally died. 



In O. pendulum, where the early divisions occur later than in O. 

 Moluccanum, in several cases the young gametophyte associated itself 

 with a fungus, as a result of which its growth was stimulated. It is 

 pretty certain that this association with the fungus is a necessary 

 condition for the further development of the gametophyte. (Camp- 

 bell (29, 7,3) -) 



The fully grown gametophytes of O. Moluccanum are very delicate, 

 slender, cylindrical bodies, 5-10 millimetres in length. None of those 

 found by the writer were branched, and they were much smaller 

 than those of O. pedunculosum, figured by Mettenius ; but otherwise 

 they were very similar. In 0. vulgatum, also, the gametophyte is 

 larger, and may be branched (Bruchmann (5) ). Bruchmann found 

 that when the gametophyte in O. vulgatum was exposed to the light 

 it developed chlorophyll. The writer was unable to induce the forma- 

 tion of chlorophyll in the gametophyte of O. pendulum. 



The gametophyte of O. pendulum is much more massive than that 

 of the other species, and is very variable in form. Usually there are 

 several stout branches radiating from a common centre. The largest 

 specimen found was about fifteen millimetres in breadth. The form 

 is determined by the position of the numerous roots of the host-fern, 

 among which the branches of the OpJiioglossum gametophyte ramify. 

 The branches are very easily broken off, but at once enter upon an 

 independent existence, and this power of reproduction accounts for the 

 very great age (probably more than twenty years) which some of the 

 prothallia show. Under special conditions buds may develop which 

 further facilitate the multiplication of the prothallia. 



P. 235. The endophytic fungus, or "mycorrhiza," is especially 

 conspicuous in O. pendulum, where it is found in all but the youngest 

 parts of the branches of the prothallium. A cross-section of a branch 

 shows a broad zone of infected tissue, which lies between a central 

 pith and several layers of peripheral cells, which are nearly or quite 

 free from the fungus. 



