446 Forestry Quarterly. 



ining the amount of soil moisture are at present crude and un- 

 satisfactory and in regard to the most important problem of all, 

 the rate of possible supply or the resistance offered by the soil 

 particles to water absorption by the roots, practically nothing is 

 known. This might possibly be determined approximately by a 

 study of the easily ascertained capillary power of the soil with 

 reference to vegetation, yet it is a problem which ecologists have 

 hardly even attempted. 



Prof. Shaw's paper in the series has already been reviewed. 

 (Forestry Quarterly, VII, 194.) 



Professor Spaulding discusses the recent advance in the knowl- 

 edge of the ecological relations of desert plants and he makes 

 suggestions for future work. He shows that important results 

 come from the simplest experiments and observations when they 

 are conducted with exactness and with a definite end in view. 

 Such as these are the conditions required for the germination of 

 the seeds of the various species ; the determination of the soil 

 moisture ; the relative root development and the determination 

 of the strata of soils which the roots of apparently competing 

 species occupy; the pre-emption of the soil by various species. 



In discussing the relation of climatic factors to vegetation, 

 Transeau calls attention to the fact that in the past century sixty 

 different proposals of geographic zones and regions have been 

 published for North America alone. This shows the futility of 

 the point of view which disregards all but one or two climatic 

 factors. When one tries to apply the actual distribution of 

 plants to these zones and regions he is still further impressed bv 

 their inadequacy. Actual plant distribution through its lack of 

 uniformity, its tendency to concentric dispersal and the coinci- 

 dence of the optimum areas of many species, seems to demand a 

 larger basis for classification in harmony with the processes, 

 composition, and origin of their components. The point to be 

 recognized and appreciated is that continental zones and their 

 subdivisions are not natural organizations of plants or plant 

 formations. 



The writer points out that we have as yet almost no experi- 

 mental data, from a modern point of view, on geographic va- 

 riation as related to climate. For such experiments pedigreed 

 plants should be used. The use of seeds from the same plant or 

 branch, or even from the same fruit is not sufficient unless the 



