246 



hours of frost in a single winter; the absolute minimum reached 

 and the length of the winter, reckoned from the first frost of 

 autumn to the last one of spring." The first and third are 

 considered the most important; and Professor Shreve states 

 that the "occurrence of a single day without mid-day thawing, 

 coupled with a cloudiness that would prevent the internal tem- 

 perature of the cactus from going above that of the air, would 

 spell the destruction of Carnegiea and the parallel evidence of 

 the climatological records and of the experiments which have been 

 described appears to explain the limitation of its northward 

 distribution." 



A Cornell pamphlet by T. L. Lyon and J. A. Bizzell on a here- 

 tofore unnoted benefit from the growth of legumes states that 

 the fact that "a legume may benefit a non-legume growing with 

 it, by causing the non-legume to contain a larger quantity of 

 nitrogen or protein, seems never to have been ascertained." 



Alfalfa, red clover, peas, timothy, and oats were the principal 

 plants used in the experiments described . Timothy grown ivith 

 either alfalfa or clover showed a large increase per ton (50 pounds 

 grown with alfalfa, 160 with clover) in protein content; oats 

 with peas showed a gain also. These legume-bearing soils also 

 contained more nitrates after the crops had been removed. Al- 

 falfa formed nitrates much more rapidly than clover — ■ the rate 

 being, of course, an important factor in relation to the removal 

 of nitrates by roots and by drainage. Alfalfa soils (five years' 

 growth) contained more nitrates than similar timothy soils. 

 Lime, it was demonstrated, improved the protein content of 

 alfalfa and of non-legumes. 



The United States Bureau of Education has issued a Bibliog- 

 raphy of Science Teaching (No. 446) compiled by a committee 

 of the American Federation of Teachers of the Mathematical 

 and Natural Sciences. The citations have been carefully 

 verified, and it makes a valuable contribution to science teaching. 



Pennsylvania has begun a systematic campaign against the 



