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THE AMERICAN NATURALIST [Vol. XLII 



in all the investigated species of Ophioglossaceae, and it 

 is safe to assume that it is invariably present and is 

 essential to the growth of the gametophyte. 



The writer has recently had occasion to study the be- 

 havior of this endophyte in the gametophyte of several 

 species of Ophioglossum and has described and figured 

 this somewhat at length. 5 The fungus consists of non- 

 septate, large, branched hyphae, which are strictly intra- 

 cellular, passing from cell to cell through the cell walls, 

 and they may often be traced for long distances. In all 

 of the forms that have been investigated the fungus is 

 confined to the older parts of the gametophyte, and never 

 invades the meristematic tissues nor the tissues in the 

 neighborhood of the young reproductive organs. There 

 is in the cylindrical branches of the gametophyte of Ophi- 

 oglossum a more or less definite infected zone inside the 

 superficial tissues, while the central region remains al- 

 most entirely free from the endophyte. Sometimes frag- 

 ments of mycelium are found upon the outside of the 

 gametophyte, and these may occasionally be found to 

 penetrate into the rhizoids and thus gain entrance to the 

 inner tissues. The infection, however, probably in all 

 cases takes place first while the gametophyte is still 

 composed of very few cells. This was positively demon- 

 strated in the germinating spores of 0. pendulum, where 

 only those young prothallia which succeeded in establish- 

 ing a connection with the fungus developed beyond a 

 three or four-celled stage. Otherwise they died after 

 the nutrient matter in the spore was exhausted. Second- 

 ary infections, however, doubtless take place frequently. 

 The form of the fungus growing outside of the prothal- 

 lium is quite different from that within its tissues. The 

 hyphae in the former case are more slender and some- 

 times septa may be formed, while these seem to be quite 

 absent from the endophytic hyphae. 



In material fixed with chromic acid, the structure of 



5 Campbell. Studies on the Ophioglossacefe. Ann. du Jardin Botanique 

 de Buitenzorg, XXVI, 1907. 



