IL] ITS PROPERTIES AND VARIETIES. 35 



sparse vessels characteristic of autumn wood can 

 be produced, so to speak, at will, by altering the 

 conditions of nutrition. 



It is authoritatively stated that the pines of the cold 

 northern countries are preferred for ships' masts in 

 Europe, and that the wood-cutters and turners of 

 Germany prize especially the timber of firs grown at 

 high elevations in the Bavarian Alps. Now the most 

 striking peculiarity of the timbers referred to is the 

 even quality of the wood throughout : the annual 

 rings are close, and show less of the sharp contrast 

 between thin-walled spring wood and thick-walled 

 autumn wood, and it has been suggested that this is 

 due to the conditions of their nutrition, and in the 

 following way. The trees at high elevations have 

 their cambium lying dormant for a longer period, 

 and the thickening process does not begin in the 

 lower parts of the trunk until the days are rapidly 

 lengthening and the sun's rays gaining more and more 

 power : the consequence is that the spring is already 

 drawing to a close when the cambium-cells begin to 

 grow and divide, and hence they perform their func- 

 tions vigorously from the first. 



One of the most interesting experiments in this 

 connection came under my observation during the 

 summer of 1887. There is a plantation of larches at 



D 2 



