PERIODICAL LITERATURE 



639 



Table 9.— Comparative transpiration losses from unit areas of surface of broad- 

 leaved and evergreen trees. 



Abies grandis, pinus niurrayana and acer saccharinum (G out of 12) 

 are recorded as winter killed. Pinus ponderosa, Picea engelmanni, 

 and Pseudotsuga mucronata (taxifolia) lost some or all of their leaves, 

 but resumed growth the following spring. 



The following is quoted from the conclusions : 



"A consideration of the foregoing data leads us to some conclusions 

 quite the converse of statements generally current in ecological- 

 physiological literature. Perhaps the most important of these are the 

 facts shown to hold under the conditions of these experiments ; first, 

 that broadleaved trees under late summer conditions have no greater 

 and indeed often a smaller transpiring power, area for area, than 

 conifers ; and secondly, that the water losses of coniferous trees during 

 the winter months are relatively no greater with the needles intact than 



are the losses from deciduous trees after the leaves have fallen. 

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"That winter losses from the same leaves that transpired so freely 

 tlie preceding fall and again in the following spring are so small is 

 certainly testimony of the ecological efficiency of coniferous leaf 

 structure for reducing water losses. Whether this is due entirely to 

 stomatal closure, or, as seems more probable, is connected with chem- 

 ical changes in cell contents as well, remains to be determined. Such 

 work as that of Miyake (15) on the food making of coniferous leaves 

 in winter and Ehlers (5) on temperature is rapidly throwing consid- 

 erable light upon the winter activities of coniferous trees." 



By way of comparison, it is of interest to cite the results of experi- 

 ments with conifers at the Fort Valley Experiment Station during the 

 winter of 1919-1920. Sealed pots containing Pinus ponderosa, var. 

 scopulorum, Pinus aristata, Picea engelmanni and Pseudotsuga taxi- 

 folia were kept imbedded in snow and ice throughout the winter, with 

 the primary object of ascertaining the relative susceptibility of differ- 

 ent species to winter killing. Trans])iration data for the entire period 



