70 



PERIODIC PHENOMENA OF VEGETABLE LIFE. 



whole season ; and as to the highest lichens, where the rocks are 

 not too abrupt, that is very frequently the case ; they have the 

 power of preservation under the snow for a very long time 

 without losing their vital faculties. * 



On account of the great length of the period during which 

 the ground is covered with the winter snows, the relation to 

 each other of the different seasons alters considerably at great 

 altitudes. The winter comprises by far the greatest portion 

 of the year, summer comes next in point of duration, spring 

 becomes very much shorter, and still more so autumn, which is 

 generally very rapidly put an end to by the fall of early snows. 



For each individual plant, the time which intervenes hetween 

 the flowering and fruiting, for instance, shows great differences 

 according to altitude, f It is, in general, long in the elevated 

 regions; for the deficiency of heat necessarily delays the ripening 

 of fruits. As examples, I will mention the Cherry, Winter Rye 

 and Barley, for which the following means are the result of a 

 great number of observations. 



NUMBER OF DAYS BETWEEN THE TIMES OF FLOWERING AND 

 OF RIPENING FRUIT. 



For the Cherry, the interval between these phenomena is greater 

 than for Rye and Barley ; so the differences according to elevation 

 vary more in the case of the former, than in the two latter : a 



* Premature ice is much more injurious to vegetation than snow ; when 

 from the oscillation (that is, the variations in length and breadth) of glaciers, 

 spots are left free either on their lower extremity or on their sides, these 

 spots remain for a long time without vegetation, although generally 

 situated below the limit of perpetual snow. The motion of the glacier 

 itself is not however without influence in this respect, as it destroys the 

 roots and germs of previous plants. And new plants, even mosses, 

 establish themselves with great difficulty on the smooth rocks and rocky 

 fragments left on the edge of the glacier. 



t There may be some exceptional cases where the length of time from 

 the flowering to maturity is not sensibly increased, but these cases have not 

 as yet been determined with certainty. Those species which will grow up 

 to a great elevation are the best suited for these comparisons. 



