124 BOTANICAL GAZETTE [februarv 



been dissolved by the NaOH but had not been hydrolyzed, or 

 that the magnesia mixture failed to give quantitative precipitations 

 of the P0 4 ions under the conditions of the experiment. 



Table IX reports a study of the solubility of the F 3 nitrogen in 

 i percentage NaOH. The results are inconclusive, but are reported 

 for the sake of completeness. 



The calculations reported in table XIII are self-explanatory. 

 It will be noted that the average proportions of framework material 

 are considerably higher at the lower temperature. Microchemical 

 examination of median cross-sections of the leaves and of the culms 

 showed a greater degree of lignification of the xylem bundles at the 

 lower temperature, a fact of added significance. Lignification of 

 the vessels in the culm adds greatly to the strength of the stem. 

 Referring to the enormous differences in growth habit as shown in 

 the figures, we may conclude that the upright habit at the lower 

 temperature is due to: (i) a greater proportion of culm to leaf; 

 (2) a greater proportion of skeletal material in the leaf; (3) a greater 

 degree of lignification of conductive tissues in both leaf and culm. 

 These obvious anatomical facts, however, are but the expression 

 of a difference in metabolic equilibria, especially the nitrogen- 

 carbohydrate ratio. 



Discussion 



The experiments reported in this paper, as well as the results 

 of earlier investigators, reopen the question as to just what is meant 

 by an optimum germination temperature. The classical investi- 

 gations of Haberlandt on germination temperature place the 

 optimum at the temperature which most quickly permits the 

 emergence of the radicle and plumule; in fact, practically all germi- 

 nation studies have been based upon this as the optimum. These 

 optimum temperatures, at least for the cereals, are evidently too 

 high to insure a future normal development. The writer believes 

 that the course of development is to a large extent predetermined 

 at a very early stage in the development of the plant by the chemical 

 equilibria within the seedling, especially the nitrogen-carbohydrate 

 ratio. These equilibria within the plant, like chemical reactions 

 in vitro, are conditioned by the temperature and concentrations 

 of the reacting substances. It seems likely that a high temperature 



