Periodical Literature. 621 



the buds are perfected in the summer and their volume increased 

 at the expense of reserve materials. 



Small temperature rises (light is not an element of influence) 

 above freezing point induce their opening, especially if the higher 

 temperature continues for some time. The later bloomers rely 

 upon the food materials prepared in the flowering year and 

 hence upon the foliage of that year. Here light plays a great 

 role as it is needed for assimilation. The later the blooming the 

 more dependence on the presence of foliage to prepare food ma- 

 terials. In all cases temperature and humidity are the main 

 factors. 



Plants flower preferably on given dates fixed by heredity. The 

 climatic conditions of fall or winter are without recognizable in- 

 fluence on the flowering in the following spring and summer. 

 The second flowering in summer or fall is said not to be depend- 

 ent on the climatic conditions of the preceding season. Sun- 

 spots have no influence on flowering. 



To permit a plant to flower it must have passed a rest period 

 to make it responsive to outer stimuli. While such plants can be 

 brought to premature flowering by immersion into warm water 

 of 28° to 30° C, those that have had no such rest period will 

 not respond to that treatment. 



Die periodischen V egetationserschcinungcn in ihren Beziehimgcn zu den 

 Klintatischen Variationen. Centralblatt f. d. g. Forstwesen. August, 

 September, 191 1. Pp. 420-422. 



At the University of Chicago, Fuller is 

 Bz'ap oration studying the rate of evaporation within var- 

 Bxperiments. ious plant associations on the Lake Mich- 

 igan sand dunes and adjacent areas. From 

 a preliminary report of his investigations, we find that the pioneer 

 tree association on the dunes is dominated by the Cottonwood ; 

 older dunes by conifers. Jack Pine in the case of the one studied. 

 In time the conifers are displaced by Black Oak and White Oak. 

 The amount of evaporation beneath these three kinds of stands, 

 as measured by the porus-cup atmometer was compared with that 

 beneath the climax beech-maple forest. 



Upon a percentage basis, the average rate per day through- 

 out the season in the beech-maple forest taken as a unit, the 

 comparative evaporation rate in the oak dune is 127%, in the 



