FOBE8TRY. 257 



In height of about 6 in. per year. Mature trees grown in the open rarely exceed 50 

 ft. in heighl and are irregularly shaped. 



Pure stands are comparatively tare. In one instance a pure stand of 18-year-old 

 trees, covering about an acre, ranged in height from 10 to L6 ft. A sample square 

 rod 12 yards distant from the parent tree showed 27 young trees, of which 11 were 

 dominant. In mixtures the pitch pine must be a dominant tree, and remain so if it 

 [g to exist. Under such conditions the trees grow from 60 to 70 ft. in height and in 



Bome cases 80 ft. The dominant pitch pine found in hard w Is is of most economic 



value. 



The pitch pine appears to he most intolerant to shade during the early years of 

 growth. Observations indicate that trees 12 to 25 years of age growing singly require 

 an area \\ hose radius is from 8 t" 1<> ft. The tree grows on nearly all kinds of soil, 

 hut prefer- a sandy, loamy, or even a st..nv soil to the heavy clay soils. It appears 

 to he especially resistant to the attacks of tire .hie to its unusually heavy hark, which 

 in mature trees is often as much as L.5 in. thick. It is used sylviculturally as a Qurse 

 for white pine. Trees 8 years old bearing cones were observed. These cones, how- 

 ever, were sterile. 



The cones on trees I'd to 30 years of age produce some fertile see.l^. The seed years 

 appear at intervals of from :; to ."> years. The cones are very persistent and the seeds 

 frequently ripen and fall from the cone while it i- still on the tree. Wind appear- 

 to be the most important agent in the distribution of the seed. This pine -ends up 

 spnmts from the old stump. Tahles of volume and growth are given showing the 

 stem analyses, a- regards volume and rate of growth, of 67 pitch pines cut during the 

 summer. 



Cultivation of the cinchona tree in Java, K. M. Bartleman I Mo. Const dor Rpts. 

 [U. S.~\, 1905, No. 296, pp. 159, WO).— The methods of cinchona tree culture in Java 

 are described. 



Zapote tree and chicle gum, A. J. Lespfnasse i Mb. Consular Rpts. [«*. ,s'.], inn.',. 

 No. 296, pp. 241-248 . — The wood of the zapote tree is described and an account given 

 of the chicle industry in Mexico. 



Continuous tapping of the zapote does not appear to seriously injure the tree pro- 

 viding the incisions are not too deep. Trees have been tapped l'-~> years, at the end 

 of which time they produced only from 0.5 to 2 lhs. of sap. When allowed t<» rest 

 5 or ti years they produced from :! to 5 lhs. New trees produce from 15 to 25 lbs. of 

 sap according to size. In order to produce the latter amount a tree would have to 

 square about - ft. and he from •_'•"> to 30 ft. high. 



Guayule and its economic importance, R, Endlich | Tropenpflanzer, 9 (1905), 

 No. 5, />/>. 283-247). — A description is given of the guayule rubber plant I Parthenium 

 argentatum), which grows wild in Mexico and which is being harvested and used 

 commercially for the production of rubber. 



The methods of extracting rubber from this plant are briefly described and the 

 possibilities of the industry discussed. At present the dried plants bring from (30 

 to $40 per ton. Recently methods for manufacturing the rubber from the plant have 

 been so improved that besides the water content of the rubber there is but from in 

 to l.". percent of foreign substance. The dried plants furnish from s t.» il> per cent 

 of rubber, depending upon the amount of moisture which they contain. 



The author inures that a commercial factory which would turn out L, 000 kg. of 

 guayule rubber per day would require from 10,000 to 14,000 kg. of dry raw material. 

 This would require the materia] from 16 to 24 hectares daily, or from 6,000 to 8,500 

 hectares during the year. The plant grows very slowly and after it ha- once been 

 cut off requires about H» years to again reach suitable size for cutting. These calcu- 

 lations give an idea of the extent of land required to make the growth of this plant 

 profitable commercially. 



