436 GROWTH OF PLANTS 



line pyrogallol. In 0.3 per cent oxygen 32 per cent CO2 retards the growth 

 of the mycehum only slightly. 



Backus^ studied Coccomyces hiemalis Higgins, the cherry leaf-spot 

 pathogen, throughout its life history in the cherry leaf, and also in artificial 

 culture. Special emphasis was placed on the mechanism by which the 

 ascocarp originated, whether by heterothallism or homothallism. Micro- 

 conidia were found attached to trichogyne-ends but fusion was not ob- 

 served, nor could microconidia be germinated. The disposition and behav- 

 ior of the structures led to the conclusion that the ascocarp is homothallic. 

 The results are fully discussed in relation to the work of many investiga- 

 tions of autonomous Ascomycetes, lichens, Rhodophyceae, and various 

 fungi in which similar problems appear. 



Effect of Nitrogenous and Carbohydra.te Reserves on Growth 



OF Seedlings 



Reid ^^' ""^^ '''• '^2 varied the relative amovmt of nitrogenous and carbohy- 

 drate material supplied to growing seedlings first by selecting high and low 

 protein and high and low carbohydrate seeds, by removing CO2 from the 

 air supplied to growing seedlings, or by raising the CO2 in the air more 

 than ten-fold to 0.4 per cent, and by withholding nitrates from or adding 

 them to the nutrient solutions. High oil reserves in seeds were aligned with 

 high carbohydrate reserves. In the case of wheat and corn it was possible 

 to get high and low protein and high and low carbohydrate varieties within 

 the same species. Other seedlings used in the studies were: sunflower, 

 tomatoes, barley, peas, beans, soybeans, and muskmelon. 



In general, when the reserve available to the growing seedling was high 

 in carbohydrates in proportion to nitrogenous material, the roots were 

 large in proportion to the tops; and when the nitrogenous reserves were 

 high in proportion to the carbohydrates, the tops were large in proportion 

 to the roots. High CO 2 concentration in the air increased the carbohydrate 

 supply, and nitrates in the nutrient solution increased the nitrogenous 

 reserve. Seedlings from seeds with high carbohydrate but low nitrogen 

 reserves give more increase in growth with nitrate addition than with 

 extra CO2 in the air; and the reverse is true of seedlings from seeds with high 

 nitrogen in proportion to carbohydrate reserves. Seedlings with low nitro- 

 gen reserves and without nitrates added to the nutrient solution tend to 

 accumulate much carbohydrate and have thicker-walled xylem vessels and 

 greater lignification of bast fibers. Contrary to other investigators, the 

 author finds that excessive amounts of carbohydrates in seedlings limit 

 growth and chlorophyll development unless nitrates are added to the 

 nutrient solution. 



Analytical Methods 

 Ashing plant tissue. Ashing plant tissue ''^ in a combustion tube fur- 

 nace under one pound oxygen pressure at 450° C (842° F) for 8 to 16 hours 



