130 EXPERIMENT STATION RECORD. [Vol.40 



of from 6,000 to 9,000 ft., marking approximately the limits of yellow pine. 

 Climatic conditions and soil moisture are discussed in this connection. 



The role of climatic conditions in determining the distribution of vegeta- 

 tion in the United States, B. E. Livingston and F. Shreve (Carnegie Inst. 

 Washington Year Book, 16 (1917). p. 95). — This investigation is said to have 

 shown conclusively that the principal types of vegetation in the United States 

 are controlled as to distribution by those moisture conditions which are related 

 most directly to the maintenance of equilibrium between absorption and trans- 

 piration in individual plants. 



Evaluation of the temperature of the soil as an environmental factor, 

 \Y. A. Cannon (Carnegie Inst. Washington Year Book, 16 (1917), pp. 91, 92). — 

 A study of the influence of soil temperature on growth, employing as an indi- 

 cator the development of Covilh a tridi ntata, which is said to be very sensitive 

 in this respect, is claimed to show that the soil temperature at a depth of 30 

 cm. (11.8 in.) at Tucson, Ariz., is about eight times as effective for root growth 

 of Covillea as at the same depth at Carmel. This is a <liflVrence sufficient to 

 account for the survival of a species in one locality and its failure in another. 



Osmotic concentration of tissue fluids in relation to geographical distribu- 

 tion, J. A. Hakkis (Carnegie Inst. Washington Year Hook. It; (2917), pp. 88, 

 89).— Studies previously reported (E. S. R., .::. pp. 47. 032; 3S. p. 125; 39, p. 

 29) and in progress on sap concentration have at present for their ultimate 

 object the completion of a reconnoissance of the sap properties of the vegeta- 

 tions of typical phytogeographical regions, a list of which is given. 



Vegetable saps (Carnegie Inst. Washington Year Bonk. 16 (1917), pp. 131, 

 132). — The director of the department of exi>oriinental evolution states that 

 studies by Harris and Lawrence have shown that sap concentration in trees in- 

 creases from lower to higher levels, and it is considered probable that this in- 

 crease of concentration with elevation is a cause of Bap ascent. A correspond- 

 ence appears to exist also between sap concentration ami environmental con- 

 ditions and between concentration and the successive terms of the series trees, 

 shrubs, half shrubs, perennial herbs, ami winter annuals. Phanerogamic para- 

 sites (Loranthacese) have in general higher osmotic pressures in their saps than 

 their hosts. 



Some marine mangroves show, as regards sap concentration, osmotic pres- 

 sures at least as high as 50 atmospheres. Certain mangroves growing in nearly 

 fresh water show not over half that concentration. These facts, it is thought, 

 may possibly he connected with the adaptation of mangroves to growth in salt 

 water. 



Studies on the development and nutritional physiology of some Chloro- 

 phycete, H. Nakano (Jour. Col Sei., Imp. Univ. Tokyo, -}0 (1917), Art. J. pp. 

 JI). i>ls. 3, figs. 9). — A study has been made involving pure cultures of three 

 new physiological races and two new morphological species of algae. All of 

 these are said to be able to give, when cultivated with Azotobacter, a larger 

 amount of nitrogen than is given by Azotobacter alone. This fact is held to 

 point to a symbiotic relation between Azotobacter and the alga? in question. 



Yellowing in these alga? is said to result from the diminution of chlorophyll 

 while the yellow coloring matters persist, the yellowed cells being richly sup- 

 plied with fat or grains of amylodextrin. The factors involved are a plentiful 

 supply of assimilable carbon, deficiency of nitrogen, intense Illumination (red 

 rays), optimal temperature, and alternate presence and absence of air. The 

 conditions for restoration of normal green color are renewed supply of nitrogen 

 compounds (several forms named), moderate light intensity (blue rays) or 

 e\eu darkness, optimum temperature, and sufficient oxygen supply. 



