500 



2 degrees C, however, the elongation was (juite perfect. IMaizc had not 

 changed at 5 degrees C. and even at 8.7 degrees C. germinated ver)' slowly 

 and imperfectly. Vetches and rape seed had germinated at o degrees and 

 exhibited a development of the seed leaves v^-orth mentioning, while peas in 

 greater numbers, and lupins and beans in smaller amounts, had elongated 

 the root body, to be sure, but had not developed the aerial axillar)^ part. Of 

 seeds which had germinated at 2 degrees C, flax was more sensitive than 

 rape seed, which germinated at approximately o degrees, but did not advance 

 developmentally or show growth worth mentioning until given a noticeably 

 higher temperature (8.7 degrees C). Peas and clover were found to stand 

 next to vetches. They put forth a root and leaf at an average temperature 

 of 2 degrees C, while beans and lupins needed at least 3 degrees C. for this. 

 Asparagus developed slowly at 2 degrees C. For the carrot, approxi- 

 mately 3 degrees seemed to be necessar)-^ for germination, and for the beet 

 root about 5 degrees C. was needed. 



It is not necessary to state here in detail that naturally the length of 

 time of germination increases in proportion to the amount of temperature 

 variation from the optimum of germination, but attention might be called 

 to the fact that such germination experiments with the lowest possible tem- 

 perature could lead to the growing of varieties hardy to frost. In all the 

 seeding experiments uneven germination is found. It may be possible that 

 those seeds which have first germinated at such low temperatures give plants 

 which have a lesser need of heat for all their life processes than do other 

 individuals of the same groups. 



Kirchner's experiments^ show that not only the initial stages of ger- 

 mination can take place normally at such low temperatures but also that a 

 further growth in length is made possible. Kirchner found mustard, rye, 

 wheat, peas and hemp growing, as seedlings, for some time at temperatures 

 which lay but little above o degrees C. To be sure, plants with a greater 

 need of heat still show some growth in length when carried over into a low- 

 temperature ; but this growth can be explained only as the gradual dying 

 out of the oscillations of the energy of growth obtained under earlier, more 

 favorable conditions. 



Kerner- has observed with Alj)inc jilants that they can even blossom at 

 o degrees. The melting water trickling into the soil from the snow fields 

 is able so to stimulate the life activity of such plants that the heat produced 

 by their respiration is able to melt the ice crust when it is even 2 to 5 cm. 

 thick, so that the green organs reach the open air (Soldanello). 



Autumn Coloration. 



The coloring of the leaves in the autumn is not always the same for the 

 same variety. It seems that the difference is caused by the habitat of the 

 individual. In general two types can be distinguished; either a perfectly 



1 4. Ver.s. deutsrher Naturfor.scher u. Arzte zu Salzburg, p. 75 d. Berichtes. 



2 Berichte d. naturwissenschaftl.-mediz. Vereins zu Innsbruck, Sitzung vom 

 15. Mai 1873, cit. Bot. Z. 1873, p. 438. 



