499 



way. The stone pine (Pinus Pima) requires at least 7 degrees C. In 

 Potamogeton, the breaking down of carbon dioxid is found first between 

 10 to 15 degrees C. ; on the other hand, in ValHsneria even above 6 degrees C, 

 and in the leaves of the larch at 0.5 to 2.5 degrees C, and in meadow grass 

 at 1.5 to 3.5 degrees C. The movement of the leaves of the sensitive plant 

 {Mimosa pudica) first occurs when the temperature of the surrounding air 

 exceeds 15 degrees. 



The difference in the amount of heat required by different plants is 

 Fhown best by the observations made on the germination of seeds in ice. 

 Uloth^ found, for example, that seeds of wheat and maple {Acer platanoides) 

 germinated in ice and bored their way deep into the ice, which they melted 

 by the heat developed during germination. The fine lateral roots of the 

 wheat had traversed ice pieces one-eighth of a meter in thickness. Later 

 experiments- showed the same observer that several of the Cruci ferae 

 {Lapidium ruderale and L. sativum, Sinapis alba and Brassica Napus), oats, 

 barley and r\'e, as well as other grasses, had germinated in large percentages. 

 In barley and oats the percentage of germination, however, was noticeably 

 less than in wheat and rye. Of the Papilionaceae, 80 per cent, of the peas 

 had germinated in the ice-cellar and 12 per cent, of the lentils; 60 per cent, 

 of sown parsley seeds showed germination. Incited by these observations, 

 Haberlandt^ later undertook further experiments with sowing the common 

 agricultural seeds in cases which were kept constantly at a temperature of 

 zero degrees to i degree C. by means of ice. After a month and a half, rye, 

 hemp {Cantelina sativa), red clover, alfalfa, vetches, peas, and bastard 

 clover showed the beginnings of germination. After four months, how- 

 ever, a further development of the little roots could be proved only for 

 mustard, camelina (or gold of pleasure), bastard clover, red clover and 

 alfalfa, while wheat, barley, oats, ray grass, buckwheat, beets, rape, poppy, 

 white clover, beans, etc., did not reach germination. Of all the plants, 

 alfalfa had strikingly proved most favorable. 



These results, in regard to grain varieties, stand in very marked con- 

 tradiction to Uloth's conclusions and also to the results of experiments 

 which Hellriegel* has published. Of all the plants tested, winter rye was 

 proved decidedly to require the least heat. With an almost constant tem- 

 perature of o degrees C. (within the six weeks period of the experiments 

 the temperature only a few times slightly exceeded this, reaching i degree 

 C), this plant developed its leaf and root apparatus perfectly normally. 

 Winter wheat was proved to need somewhat more heat because of the small 

 size of its germinating plants, and, agreeing with Uloth's results, to a still 

 greater degree, barley and oats, which at o degrees C, only slightly devel- 

 oped their rootlets, while unable to force the leaf cone out of the grain. At 



1 Fuhlins's Neue landwirtsch. Z. 1S71, p. 875. 



2 Flora 1875, p. 266. 



3 Wissenschaftl. praktische Unter.suchung-en auf d. Gebiete d. Pflanzenbaues. 

 Wien 1875, I, p. 109ff., 117. 



4 Beitrage zu den naturwissenschaftl. Grundlagen des Ackerbaues. Braun- 

 schweig, Vieweg 1883, p. 284-304, 



