200 



THE AGRICULTURAL NEWS. 



June 21, 1913. 



EDITORIAL NOTICES. 



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Jiiiriciiltural ^leiufi 



Vol. XII. SATURDAY, JUNE 21, 1913. No. 291. 



NOTES AND COMMENTS. 



Contents of Present Issue. 



The subject treated of in the editorial in this 

 number is Elasticity of Demand. The considerations 

 concern mainly the relation of this economic force to 

 fluctuations in the values of raw material. 



(Jn page 195, the recently published report on 

 .sugar cane experiments in the Leeward Islands, 

 1911-12, is reviewed, in such a manner as to indicate 

 the more valuable results that have been obtained. 



The concluding article on problems in propagation 

 ■by cuttings is continued from the last issue of the 

 AgriciUtural Neia^, on page 197. 



(Jn page 19S will be found presented, in a concise 

 manner, recent views on the Tropical University 

 question. 



Under the caption Book Shelf, on page 199, will 

 be found a review of an important work describing 

 agricultural conditions in Mozambi^jue. 



Insect Notes, on page 202, comprise information 

 on the subject of insects liable to dissemination in 

 shipments of sugar-cane. 



On Page 206 will be found Fungus Notes which 

 describe recent work on the Panama disease of bananas 

 in Jamaica. Reference is also made to several new 

 exotic fungi. 



Superiority of Tin Cans over Pots for Seedling 



Plants. 



An ingenious investigation into the circumstance, 

 observed in Hawaii, that seedling plant,-; like mango 

 and avoiado, grow better in tin cans than in earthern- 

 ware pois, is described by E. V Wilcox in Press 

 Bulletin No. 41 of the Honolulu E.\-periment Station. 



For the practical propagakior the results of the 

 investigation are of very considerable importance, and 

 of a characifr highly sugtji-stive. 



As a working basis it was supposed that the two 

 factors involved were differences in evaporation, and 

 stimulation due to tin and solder in the cans. In the 

 course of the experiments it was found that 

 the average evaporation from pots was exactly two and 

 a half times greater than that from the tin cans, 

 though as might be expected, in sunshine, the relative 

 increase was greater for the tins owing to the 

 more rapid penetration of heat. The soil in a pot 

 was found to be more exposed to evaporation than 

 even the greater surface area would indicate. A more 

 interesting result was the discovery that with the 

 ordinary pot, •52-3 per cent, of the evaporation takes 

 place through the top. and 47 7 per cent, through 

 the side. Funher determinations showed that the 

 evaporation from a given area is So times as fast through 

 a free surface of soil, as through the side of the pot. 



A continuation of the investigation consisted in 

 the growing of seedling plants in pots of varying 

 porosity, and the height and vigour of the plants 

 increased in regular gradations as the porosity dimin- 

 ished. It was next found desirable to determine the 

 loss v( water by transpiration. 



This was done by the r=niarkably simple method 

 of substracting the loss in the tins and pots without 

 plants from the loss from the tins and pots with plants. 



The results showed that the total loss from two 

 months old plants in pots was approximately the same 

 as that from two months old plants in tins, the explana- 

 tion being, of course, that the greater loss by transpir- 

 ation from the larger and more vigorous plants in the 

 tins, balanced the greater loss by evaporation from the 

 soil in the pots. Leaf measurement showed that 

 transpiration was 16 times greater in the case of the 

 plants in tins, and therefore they might obviously be 

 considered as growing more vigorously. 



The great advantage of using tin cans rather than 

 porous pots seems to rest in the fact that in tins it is 

 easier to maintain a nearly constant moisture content 

 without a rapid drying of the soil about the growing 

 roots which naturally follow the horizontal water move- 

 ment towards the side of the pot. 



Finally, in regard to the influence of the presence 

 of salts of tin and zinc, plants grown in untreated cans 

 did better than those grown in cans of which the inter- 

 nal surfaces had been waxed. This result together with 

 the fact established, chemically, that very dilute 

 solutions of tin and zinc salts do have a stimulating 

 influence on plant growth, would appear to be good 

 evidence in support of the conjecture that the presence 

 of these salts in the tin can, is a second beneficial factor 

 which is absent in the cass of its rival the earthcvn- 

 ware pot. 



