TEMPERATUME. 



187 



Pea 26° Cent. (78.8° Fahr.). 



Wheat (winter var.) 34° " (92.7° " 



Indian corn 34° " (92.7° " 



Scarlet Bean 34° " (92.7° - 



In Sachs' and others' observations upon the growth of 

 roots, it was found that tlie most rapid growth took place 

 for different plants at the following temperatures : 



Scarlet Bean 26° Cent. (78.8° Fahr.). 



Pea 26.6° 



Flax 27.4° 



Wheat (winter var.) 28.5° 



Barley (summer var.) 28.5° 



Indian corn 34° 



(79.9° 

 (81.3° 

 (83.3° 

 (83.3° 

 (92.7° 



In the deposit of reserve material there can be no doubt 

 that metastasis often takes place at lower temperatures than 

 assimilation ; thus the storing of starch in the potato tubers, 

 and in many other subterranean stems and roots, takes place 

 in the soil which, at the time, is much cooler than the air. 



In the growth of many plants in early spring, at the ex- 

 pense of reserve material in the roots or stems, the metas- 

 tatic changes often take place at quite low temperatures. 

 Thus perennial and biennial rooted plants, as many grasses, 

 thistles, parsnips, etc., begin to grow almost as soon as the 

 snow has disappeared, and the flower buds of many perenni- 

 als develop equally eai'ly — e.g., the hazel, elm, maple, liver- 

 leaf (Hepatica), Mayflower, etc. 



As regards the metastatic changes which take place in the 

 germination of seeds, we have much more definite informa- 

 tion. Sachs has determined the minimum, optimum, and 

 maximum temperatures for the germination of the seeds of 

 the following plants :* 



Keimung von der Temperature," in " Pringsheim's Jahrbiicher fiir 

 Wissenschaftliche Botanik," Vol. II. , 1860, p. 354. 

 * " Phyaiologische Untersuchungen," etc., op. cit., p. 365. 



