ToL. YII. No. 150. 



THE AGRICULTUEAL NEWS. 



29 



THE BREATHING OF PLANTS. 



A reprint of a lecture on the above subject, 

 ■delivered at the New York Botanic Gardens, appears 

 in a late number of the Journal i>f I lie Botanic 

 Gardens. The fallacy of the popular idea — taken 

 literally — that plants dififer from animals in that 

 while the latter breathe in oxygen and breathe 

 out carbon dioxide, the former absorb carbon dioxide 

 and exhale oxygen, is explained, and it is shown that 

 respiration or the absoi'ption of oxypen, with its 

 -consequent exhalation of caibon dioxide is carried on 

 by every part ot a livingr plant — leaves, flowers, stem, 

 and roots. The following extracts are from the 

 lecture in question : — 



Great <litl'ereiK-e.s exist between certain aiiniials, us well 

 as between certain jilants, but the process of respiration is 

 everywhere the .same. Even dry seeds, which certain German 

 physiologists have considered as in a condition of ' Srhrlntodt ' 

 (apparent death ), are respiring. The bouquets in our vases, 

 the celery and lettuce on our tables, as well as the trees, 

 shrubs, and herbs, indoors and out, are constantly taking in 

 oxj'gen, e-xchangiiig it in the living cells for carbon dioxide, 

 and returning the latter to the surrounding air. 



Even ill regard to the amount and rate of respiration 

 the .supposed difference between animals and plants breaks 

 down. Under favourable conditions the process niciy even 

 be more active in plants than in animals. In man the 

 -carbon dioxide produced in twenty-four hours eipials about 

 1'2 per cent, of the body weight, but in some of the moulds 

 the amount has been found to ecjual 6 per cent of the dry 

 weight of the plant. Bulk for bulk, the very active bacteria 

 may consume oxygen 'JOO times more rapidly than man. In 

 both kingdoms respiration is accompanied by an evcilution 

 of heat. 



In plants, as in animals, the rate of respiration varies 

 with the age of the organism, and with external conditions. 

 Breathing, which is the expression of respiration in man, 

 is most rapid with infants, and decreases with the approach 

 of old age. So it is with jilants, for germinating seeds and 

 young seedlings respire more rapidly than mature pilants. 

 Increase of work is accompanied with increase of respiration 

 in animals : in trees also, the process is more vigorous in the 

 spring, during the work of bud opening and putting forth of 

 new leaves and flowers. Under bodily pain or mental 

 excitement we breathe more rapidly, so also does a plant 

 that has been cut, or otherwise injured, or subjected to any 

 stimulus, as, fen' example, violent shaking.- A thermometer 

 placed in a dish of cut onions, for example, will indicate the 

 existence of a fever (due to wounding of the tissue), just as 

 surely as if placed in the mouth of a typhoid patient. 



This question is far from having a merely academic 

 interest. Practices that have been in vogue since man first 

 began to till the soil, and that must be continued as long as 



■ agriculture is carried on, depend in jiart upon the respiratory 

 function of plants. 



In reference to the operations of ploughing the soil and 

 hoeing the crops, it is not alone to get the soil into a suitable 

 physical condition that this work is carried out by the 

 farmer. The roots and other under-ground parts must have 



■ air to respire just as much as the parts above ground, but if 

 the soil is hard and compact this need is but poorly met. 

 The plough, the spade, and the hoe facilitate the thorough 

 aeration of the ground. For the same ; reason it is desirable 

 frequently to loosen the surface of the soil in the flower pots, 

 and this, in part, is why Hower pots are made of porous 

 anaterial. 



PREPARATION OF RUBBER FOR 



MARKET. 



In view of the experimental work that is in- 

 progress in many of the West Indian Islands in the 

 cultivation of rubber trees, and of the efforts that are 

 being made to place the resulting product on the 

 market in the best form possible, the accompanying 

 extracts from the last Annual Report of the Director 

 of Agriculture of the Federated Malay State.s. 

 {Islv. J. B. Carruthers, F.LS.) are worthy of note : — 



Our knowledge of the best methods of preparation of 

 plantation rubber for the market is still in the jilastic and 

 changeable stage. Biscuits have had their day, and on all 

 estates producing any quantity of rubber they have been 

 aliandoned as uiqiraeticable when large (piantities are to be 

 treated. Sheet or crepe have both their advantages, and the 

 manufacturer has learnt to appreciate their fine qualities. 

 But the goal to which the rubber planter is making in 

 relation to the improvement of his product is the preparati.jn 

 of a rubber which the buyer and manufacturer will consider 

 as good as, or better than, the finest Brazilian Para. 



The (jualities of resilience, elasticity, and durability 

 M-hich characterize the Brazilian rubber must be produced in 

 plantation rulilier, and the discovery of the means by which 

 this end can be obtsiined has been the subject of much 

 consideration, experiment, and observation both in the Malay 

 States and in Ceylon. 



Acetic acid and creosote, which, in the raso of the 

 preparation of Brazilian rubber, are added by sulimitting the 

 latex to smoke containing these sub.stances, have been intro- 

 duced in the case of plantation rubber by mixing small 

 (piantities of these two sub.stances in .solution. 



The acetic acid produces quick coagulation, and the 

 creosote is an efficient antiseptic and prevents the gixnvth of 

 bacteria which pniduce ' tackiness ' or other putrefaction nf 

 tilt' dry rubber. 



The physical treatmmt of the Brazilian Para, whirli is 

 sent home in blocks consisting of a series of thin films of 

 rubber, each dried so that it contracts and produces an 

 automatic pressure, is most probably one of the factors which 

 give it its resilience and elasticity. This has been imitated by 

 artificial pressure, by means of a scew press, of the rubber into 

 lilocks of approximately the same density as the Brazilian 

 Para. The presence of a cfirtain percentage of water in the 

 Brazilian block may be one of the factors which add to its 

 good qualities, and the retention of a percentage of water, 

 instead of the complete drying which had jireviously been 

 carried out in the Federateil jMalay States rubfier, has now 

 been tried with success. AVet block rubber sent home from 

 jNIalay and Ceylon was received with satisfaction by the buyer, 

 and fetched a higher price than any other plantation rubber 

 on the same day. 



The manufacture of wet block rubber, i.e., rubber which 

 after being coagulated and a-septicised is at once pressed into 

 blocks, is a great saving of time, and in the .space of plant 

 required. Rubber can be preiiared for shipment a few hours 

 after the latex has been taken from the tree. 



The block rubber travels better without tlie deterioration 

 pn route to which the other forms, having lai-ge expo.sed 

 surfaces are very liable. 



The production of wet f)Iock rubber, free from putrefac- 

 tion, of a convenient size and weight, and containing a uniform 

 quantity of water, say 10 per cent., seems at present without 

 doubt the best method. 



