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JOURNAL OF FORESTRY 



an area of 4,000 hectares, for instance, with 200 trees per hectare and 

 2 faces per tree, will require 1,600,000 cups. Under present conditions 

 the cost of cups exceeds all other outlay combined. The "swallow- 

 nest" tins, which were tried, proved unsatisfactory because of poor 

 material and defects in manufacturing. Square (right-angled) metal 

 troughs driven into notches in the trees were just as good for the adze 

 method. It is suggested that cheap wooden cups may be devised. 



Biehler of Rastatt reports the following results of his studies of 

 working Scotch pine : 



I. Influence of sice of crozvn. In general the better developed the 

 crown, the better the assimilation and nourishment and consequently 

 the yield of resin. There was, however, great variation in yield of 

 individual trees, irrespective of crown development. About one-fourth 

 of all trees were good yielders, three-fourths poor. The proportion of 

 good yielders increased with d. b. h. and with development of the 

 crowns. Thirty-two per cent of full-crowned trees were moderate or 

 good yielders, as compared with only 19 per cent of the thin or small- 

 crowned trees. The following table shows the classification bv classes 

 and yield of resin : 



2. Infncnce of soil. There was a marked difference in yield due to 

 dififerences in depth of soil. The best yielders were those whose roots 

 were in the deepest soil ; those with roots mostly in a gravelly subsoil 

 gave poor yields. Yield potentiality may be judged to some extent by 

 crown and soil. The appearance of the needles is also important as an 

 indicator. Full, succulent green foliage generally (not always) indi- 

 cates good }ield ; thin, yellowish foliage generally indicates the reverse. 

 Simple and sure indications by which the potential yield of individual 

 trees may be judged are of great importance to the industry, since by 

 this means the working of poor yielders may be avoided. 



3. Infncnce of nuniher of faces. The yield increases with the pro- 

 portion of circumference which is worked, up to certain limits, except 

 as modified by unfavorable exposure or other factors. It is best to use 

 from I. to 3 faces, according to size of trees. 



4. Infnoiccs of depth of cut. One group of five trees was cut to a 



