26 BOTANICAL GAZETTE [JANUARY 



and (3) that when low temperature is combined with poor aeration 

 the effect is very marked. 



This experiment was repeated with peas, and the same result 

 was obtained, although the effects were not so marked (fig. ij). 

 The roots in the undrained substrata were killed when they attained 

 a depth of a half inch (i2 mm ) below the surface: 



(3) In order to test the effects of drainage and of low temperature 

 on bog species, another set of cultures in peat-sphagnum substrata 

 was made. The apparatus used consisted of two flower-pots and 

 two glass dishes aproximately a foot in diameter and three inches 



XH- 



FIG. 13. Effect of the several conditions upon the development of pea seedlings. 

 All are average specimens. From photographs. 



deep (3oX7.5 cm ). A flower- pot and a glass dish were kept cool by 

 passing cold water through fifteen feet of glass tubing arranged in 

 coils, as in previous experiments. Three species were tested in these 

 conditions: two-year-old Larix laricina, Rumex acetosella, and 

 Prunella vulgaris. The first cultures were made in the spring of 

 1903 with the Rumex and Prunella. The air temperature averaged 

 about eighteen degrees. The cold substratum was maintained about 

 ten degrees lower. In the case of Rumex it was found that the 

 largest leaves were produced in the drained peat-sphagnum substra- 

 tum. Lack of drainage and low temperature both caused a reduction 

 in leaf area, and when combined produced leaves which were less 

 than half as large as those of the drained warm substratum. 



The Prunella under the same conditions showed the same results. 



