1044 JOURNAL OF FORKSTKV 



exhaustion. He states that the feeding roots of trees growing in the 

 open have an approximate span of three times the distance of the outer- 

 most twigs. Regarding (2), the writer states that soil bacteria do not 

 explain the failure of a tree species after long-continued growth on the 

 same spot, and they are not sufficient to account for all that may be 

 observed in old woodlands of a single species. Although he concedes 

 that (3) is of considerable importance, possibly secondary in causing 

 soil exhaustion for a given species, all must give way to (4), namely, 

 that the active agent that appears to bring about soil exhaustion for 

 forest vegetation is "toxic atrophy," caused by a poison which is left in 

 or on the soil during the process of plant decay. This poison left by 

 decay of every species of plant is more inimical to the young of its own 

 species than to that of any other. 



The basis for the author's conclusion is entirely empirical and with- 

 out experimental data. 



J. W. T. 



Quarterly Journal of Forestry, Vol. XI, April, 1917, pp. 88-93. 



The distribution of the redwood {Sequoia 

 Redwoods, scmpervirens) has been commonly correlated with 



Rainfall, and the summer fogs so characteristic of the coast of 

 Fog California. Cooper has recently made a study of 



redwood distribution and meteorological data. 

 The investigation covered the greater part of two years in the Santa 

 Cruz Mountains, where the redwood forest is the prevailing vegetation 

 type over considerable areas of the range. The author states that in 

 the above mountains certain areas, apparently not differing in topog- 

 raphy and soil from near-by ones which support a luxuriant redwood 

 forest, are practically without this species. He cites the Black Moun- 

 tain and Monte Bello Ridge as conspicuous examples of the former. 

 A comparison was made of the precipitation on near-by areas, some 

 without redwood and others with a heavy stand. A series of rain 

 gauges was established from the coast eastward to and beyond the crest 

 of the Santa Cruz Range. The records show a great dift'erence in the 

 precipitation at stations only a few kilometers apart, and altitude seems 

 to be the main factor in influencing the amount of precipitation. The 

 amount of rainfall at the various stations bears no apparent relation to 

 the presence of redwood. Some stations without redwood had more 

 precipitation than others where it was the dominant species. The con- 

 clusion is drawn that rainfall alone is not the deciding factor in ac- 



