266 



BOTANICAL GAZETTE 



[OCTOBER 



lake on the crest of an eroding dune which is exposed to wind 

 from all points of the compass. The water content is less at this 

 point than at lower levels and the light intensity becomes the 

 greatest, the sun striking the station about 8:00 a.m., from which 

 time it remains directly exposed until evening. The absence of 



humus and the exposure to wind 

 combine to give a high sand 

 mobility, which means a most 

 unstable kind of habitat. 



Station F (fig. 6) is located 

 in a forest, the chief tree mem- 

 bers of which are Acer, Lirio- 

 dendron, Castanea, and Prunus 

 serotina. The herbaceous under- 

 growth includes such mesophy- 

 tic species as Aralia racemosa, 

 Adiantum pedatum, Osmorhiza 

 longistylis, Viola pubescens, etc. 

 The humus at this station has 

 a depth of about 5 cm, and 

 the underlying soil is a mixed 

 morainic drift. 



Methods 



The cobalt chloride paper 

 method was employed to deter- 

 mine the relative transpiring 

 power. This method, first used 

 by Stahl (15), has been im- 

 proved and employed by subse- 

 quent investigators and is undoubtedly the one in present use which 

 is best adapted for work in the field. Whatman's filter paper no. 30 

 was used throughout this work and was treated with a 3 per cent 

 solution of cobalt chloride and prepared in accordance with the 

 method described by Livingston and Shreve (id). PreHminary 

 tests were made with the plain paper and the tricolor slips of 

 Livingston and Shreve, and as essentially the same coefficients 



Fig. 6. — Station F, showing Tilia 

 in mesophytic forest on clay soil; chief 

 plant associates: Osmorhiza, Adiantum, 

 Caulophyllum, Aralia, and Actaea. 



