186 



From an ecological standpoint, the gametophytes, and later the 

 sporophytes, of Equisetum arvense took possession of this rather 

 unusual habitat. A few scattered seedlings of angiospermous plants 

 had also come in, mostly Alisma Plantago-aquatica, the water plan- 

 tain, and some leafy moss plants and fern gametophytes had 

 developed on this substratum. Equisetum arvense was by far the 

 most common plant, however, and temporarily at least, it had actu- 

 ally taken possession of this bare area, having come in by means of 

 its spores. This is a case, then, of E. arvense as a pioneer in a new, 

 bare area. It is not impossible that the presence of iron in this soil 

 may have favored the development of these gametophytes, though of 

 course there is no evidence to support this. 



Summary 



Hundreds of gametophytes of Equisetum arvense L. were found 

 in the wild during June, growing in an open iron mine pit which 

 had been pumped free of water earlier in the year. 



Some of the gametophytes were fairly large, as much as eight 

 millimeters in diameter, more or less circular in outline, and green 

 in color. Others were much smaller, some barely visible, and they 

 were mostly brownish or black when they were found. These latter 

 seem to correspond with the male gametophytes of this species found 

 in the wild in Europe by Schratz. 



The gametophytes consisted essentially of a lower parenchyma- 

 tous tissue from which rhizoids grew into the soil and from the up- 

 per portion of which erect branches were developed which were 

 variously fringed and lobed. 



This is a case in which Equisetum arvense, by means of its 

 spores, has come into a newly exposed bare area as a pioneer and is 

 becoming established. 



Columbia University 

 New York, N. Y. 



Literature Cited 



Buchtien, O. 1887. Entwicklungsgeschichte des Prothallium von Equisetum. 



Bibliotheca Bot. 8: 1^9. 

 Campbell, D. H. 1930. The structure and development of mosses and ferns. 



Third edition. New York. 

 Eames, A. J. 1936. Morphology of vascular plants. Lower groups. New York. 



