268 Pflanzenkrankheiten. 



Cook, M. T., Some problems in cecidologv. (Bot. Gazette. 

 LH. p. 386—390. 1911.) 



The purpose of this paper is to call attention to some of the 

 Problems involved in cecidolog3^ and to their bearing on other 

 phases of biology, more especially botany. The anatomical and histo- 

 logical characters and the development of cecidia have received 

 very little attention in America. 



The most difificult and probably the most fruitful field is open 

 to the plant ph3^siologist; the character of the Stimuli which excite 

 malformation is a question well worth the attention of any group 

 of scientists. Jongmans. 



Knight, L. I. and W. Crocker. Toxicity of Smoke. Contri- 

 butions from the Hüll Botanical Laboratory 171. (Bot. 

 Gaz. LV. p. 337—371. 4 Fig. 1913.) 



The experiments were made on the etiolated epicotyl of the 

 sweet pea and included such on the effect of unwashed smoke, of 

 washed smoke, on the effect of bromine absorption on the toxicity 

 of paper smoke, on the effect of coal smoke, of the \^arious consti- 

 tuents of smoke, and of carbon monoxide. A summary oftheresults 

 is given at the end of the paper. 



The smoke from tobacco cigars and cigarettes which has been 

 thoroughl^'- washed in 15 per cent H.2SO4 and 40 per cent NaOH is 

 very toxic to the etiolated epicotyl of the sweet pea. In the case of 

 cigar smoke thus treated, 1000 parts per million of atmosphere gave 

 a triple response: reduction of rate of elongation, swelling, and 

 diageotropism of the portion growing in the impurity; 5000 parts 

 per million of atmosphere completel)^ stop elongation and produce a 

 swoUen knob, while the epicotyl remains vertical, still higher con- 

 centrations kill the epicot^i before anj^ form change occurs. 



On the basis of dry weight burned, the washed smoke from 

 cellulose paper cigarettes is even more toxic. The characters of the 

 responses produced are identical with those produced by smoke 

 from tobacco cigars and cigarettes. 



When smoke from equal amounts of cellulose paper, smoked as 

 a cigarette on one band, and burned as an open sheet on the other, 

 are compared, it is found that the former is 50 times as toxic as 

 the latter. Higher ox3'gen supply during burning greatly reduces 

 the toxicitv. A large part of the toxic gases are undoubtedlv oxidized 

 to CO.2 and H2O. 



In the cigarette smoke of cellulose paper the following gases 

 are present: carbon dioxide, carbon monoxide, acetylene, ethj'lene, 

 methane, and some higher homologues of the last three. Washing 

 out the carbon dioxide does not reduce the toxicity of the smoke, 

 nor will carbon dioxide produce the type of response produced by 

 the smoke. Carbon monoxide, acetylene, ethylene, propj'lene and 

 perhaps methane produce the same type of response as smoke. 

 Carbon monoxide is in 0.015 sufficient concentration to determine 

 the effect of smoke. It is not certain that methane is toxic at all; 

 if so, it is not in 0.00001 sufficient concentration to produce the 

 response. The other three gases mentioned are not present in the 

 smoke in sufificient quantities to be detected by ordinary gasanalysis 

 methods. Considering the magnitude of toxicity of acet\^lene and 

 propylene, it is impossible that they play any part in the toxicity 

 of paper smoke. The great toxicity of ethylene makes it probable 



