105 



during the greater part of the month, when the rate begins to rise 

 on account of the trees shedding their foHage. By the latter 

 part of September the rate of evaporation is at its lowest expres- 

 sion during the period under observation, namely, from May to 

 October, inclusive. This low rate of September forms a striking 

 contrast to the high rates of much of June and all of July and 

 August, the usual flowering period of this species. It is during 

 this period of low evaporation that the stems of the Indian pipe 

 spring up, flower and mature their fruit. 



From the above data it would seem that the Indian pipe is a 

 niesophyte, but so far from being confined to mesophytic woods, 

 is able to persist in decidedly xerophytic areas. It seems, how- 

 ever, to be confined to woods. This persistence is determined 

 by the short aerial life of the plant, and not by the formation of 

 any xerophytic structures. 



Chicago, III. 



Literature Cited 



1. Coulter, S., A Catalogue of the Flowering Plants and the Ferns and their Allies 



Indigenous to Indiana. Indiana Dept. of Geology and Natural Resources. 

 24th Annual Report, pp. 553-1002. 1899. Data concerning the Indian 

 pipe is given in pp. 867-868. 



2. Cowles, H. C, The Ecological Relations of the Vegetation on the Sand Dunes 



of Lake Michigan. Bot. Gazette 27. 1899. The oak dunes are described 

 in pp. 379-382. 



3. Schimper, A. F. W., Plant-geography upon a Physiological Basis, pp. 610-612. 



Oxford, 1903. 



4. Fuller, G. D., Evaporation and Plant Succession on the Sand Dunes of Lake 



Michigan. Transactions Illinois State Academy of Science 4: 1 19-125. 

 1911. 



. TWO NEW TERTIARY SPECIES OF TRAPA 



By Edward W. Berry 



The genus Trapa, formerly included in the family Onograceae, 

 is now made the type and only genus of the Hydrocaryaceae 

 (Trapaceae, Dumort, 1827). There are three existing species, all 

 aquatics, and all confined to the Old World except lor the naturali- 

 zation of Trapa natans L., in New England and New York. The 

 latter species is found irregularly scattered throughout central 

 and southern Europe, its area of distribution being a contracting 



