Vol. XI. No. 278 



THE AGRICULTUKAL NEWS. 



409 



A Possible Source of Rubber. 



Attention has been recently directed to a species 

 of Euphorbia (£iay)/*or6ia Zo/'//biia) which contains an 

 :tinusually large quantity of eamly-obtained latex and 

 occurs in large numbers in Hawaii. .So far as is 

 jinown, this particular specie.s of Euphorbia is found in 

 no other part of the world, being a native of Hawaii. 

 In press Bulletin No. -il of ihe Hawaii Agricultural 

 Experiment Station it is stated that the best means of 

 ■coagulating the latex is with heat or by spraying the 

 latex into alcohol. The former method appears to be 

 the preferable one. The constituents which are likely 

 to be of most commercial value are the resins, the 

 acetone-soluble resin being a prudu3t of very fine 

 texture and physical appearance. The caoutchouc- 

 like substance appears to be of an inferior quality in 

 comparison to the better grade: however, it might find 

 use as a low grade product. It is suggested that useful 

 results might accrue from the destructive distillation of 

 the wood of this tree. It is further pointed out that in 

 the event of a commercial working of the latex by 

 means of volatile solvents, the insoluble residue with its 

 40-.30 per cent, prutein would have as a means of its 

 disposal a possibility of its sale as a fertilizer on 

 account of its high nitrogen content. 



A Silkworm Tree for Rocky Soils. 



A very interesting article appears in a recent 

 ■number of the Journal d' Agriculture Tropicale, in 

 which the Tapia tree {Uapaca duxiareai.), >>ne of the 

 Euphorbiaceae, is dealt with from the point of view of 

 its value for afforestation purposes and as a host for 

 a silk worm {Bvroccra madagascariensis). The 

 tree is very common on the rocky soils of the western 

 slopes of central Madagascar. In general appearance 

 It is said to resemble certain evergreen oaks, for its 

 leaves are persistent, shiny and leathery. The Tapia 

 tree seldom grows more than 40 feet in height, and 

 its thick bark and general adaptation for dry, or at 

 least for rocky localities, should render this plant 

 ■extremely suitable for afforesting the hills and moun- 

 tains of the central plateau of Madagascar, at present 

 covered with scarcely any vegetation except hard, 

 coarse grasses possessing no value as forage. 



Added to the cumulative benefits to be derived 

 from the planting of the Tapia, is the important fact 

 that the leaves of this tree constitute the favourite 

 ' food material of the indigenous silkworm already refer- 

 red to. It is stated that a large industry exists amongst 

 the natives, who collect annually the cocoons, produced 

 without the application of cultural methods. 



It appears that the future prosperity of the 

 ::ndustry has of late years been seriously endangered 

 by the removal of an interdict which rightly put restric- 

 tions on the making of bush fires. For reasons clearly 

 ^et forth in the article under review, the burning of 

 the young Tapia wood undoubtedly increases the 

 harvest in the following year or two; but the practice 

 is a short-sighted one, because the trees are prevented 

 from reproducing themselves naturally. Consequently, 



unles3 extensive planting is carried out, it is likely 

 that in the near future a profitable industry will have 

 ceased to exist. 



The subject as a whole should prove very 

 instructive to those who are interested in such matters, 

 in the West Indies. It is not definitely known 

 whether this particular species of Tapia would thrive 

 in the West Indies, but there certainly exist con- 

 siderable areas of waste land which might possibly 

 jirove suitable for its cultivation. Moreover, the efforts 

 that are now being directed towards the establishment 

 of a silkworm industry in some of the islands should 

 lend a lively interest to the present subject from 

 a purely industrial a.sjiect: though it is not definitely 

 known whether the Madagascar silkworm would fiourish 

 under West Indian conditions. 



The Assimilation of Nitrates in Plant Cells. 



The Kj-periment Station Record, Vol. XXVII, 

 1912, reviews recent work on this subject by O. Loew. 

 Considei-ing the questions of: (1) what is the first 

 transformation product of the nitrates in the manu- 

 facture of protein, and (2) what factors operate in the 

 reduction of such nitrates, the investigator does not 

 agree with the general opinion that hydroxylamine is 

 formed and that light is necessary as a source of energy 

 for the reduction process. The experiments are 

 claimed to show that: (1) contact with platinum 

 sponge is sufficient in the absence of light to 

 reduce magnesium nitrate with glucose in an over- 

 saturated solution of potassium hydrate, or to reduce 

 potassium nitrate in solution with dextrose, a process 

 analogous or similar to one that goes on in the living 

 cell; (2) the absence of light did not prevent, nor did 

 access of light accelerate, the reduction of sodium 

 nitrate in the development of the saprophytic fungus 

 I'enicilliuiii (/laucuia in a nutrient medium with 

 glycerine; (.3) in various roots kept growing in a cool 

 and totally dark chamber the nitrates were steadily 

 decreased in quantity with a corresponding increase of 

 protein: (4) young etiolated barley plants removed 

 every trace of nitrate from a nuti'ient solution in the 

 absence of light with increase of protein, while the 

 controls showed strong nitrate reaction. The con- 

 clusions based on these results are briefly: (1 ) that the 

 splitting up of nitric acid with the evolution of nitrogen 

 peroxide under the influence of light has its parallel 

 and equivalent in energy developed by the breaking- 

 down of carbohydrates in the absence of air with the 

 evolution of carbon dioxide (intramolecular respiration); 

 (2) that if hydroxylamine were formed, its toxic influ- 

 ence upon the cells would reveal its presence: (3) that 

 the requisite energy for the more difficult work of 

 reducing sulphates is derived from changes in the 

 living protoplasm initiated to some extent by changes 

 in the composition of the proteins in the living cells. 



Finally, it is believed that most roots are obliged 

 to utilize their nitrates in the absence of light, and 

 they are probably not carried to the leaves for reduc- 

 tion before utilization. 



