the Poismious Gases on Vegetables, 145 



remarked that half a cubic inch in a thousand times its vo- 

 lume of air began to affect another mignonette plant in an 

 hour, and killed all the leaves in twenty hours ; that the plant, 

 though then tak^n out with its stem erect, soon died ; but 

 that the leaves were not damp or acid, as in the former in- 

 stances. Various inferior proportions were tried with similar 

 results, till at length the following experiment was made : 



A fifth part of a cubic inch of hydrochloric acid gas was 

 mixed with three inches of air in a long jar, and placed under 

 a glass receiver of the same size and form, and with the same 

 precautions to secure a gradual and thorough mixture, as in 

 the experiments with the sulphurous acid : The plants chosen 

 were a healthy laburnum tree five inches tall, and a little larch 

 tree. In nine hours the edges of some of the laburnum leaves 

 appeared to be curling inwards ; in twelve hours this eflfect 

 was unequivocal: As the latter examination was made by candle 

 light, we could not say positively whether the colour had faded. 

 In twenty-four hours the leaves had all acquired a dull-gray- 

 ish green colour, and dry appearance, and their edges were crisp- 

 ed and curled. The crisping effect increased during the next 

 twenty-four hours, after which the plants were removed into 

 the open air of the room. The lower leaves were evidently 

 most affected, and some of them even dropped their leaflets 

 when the plant was shaken ; none, however, had escaped, ex- 

 cept a young half unfolded one at the top ; all the rest seemed 

 quite dead. As in the case of the sulphurous acid, so here 

 the crisping and curling of the leaves increased rapidly after 

 the removal of the plant from the jar; an effect which is 

 probably to be ascribed to the more rapid evaporation of 

 their moisture, no longer renewed from the leafstalks. The 

 larch plant, whose changes could not be properly seen in the 

 jar, on account of its colour being nearly the same in its natu- 

 ral, as in its withered state, was found, on close examination, 

 to be wrinkled and dry, particularly on the lower leaves, and 

 on the tips of them. Neither of these plants, however, died ; 

 the unfolded leaves were all destroyed, but the buds gradually 

 expanded themselves, though nipped on the tops. 



This gas must therefore be very injurious to vegetable life, 

 since so small a quantity as a fifth of an inch, although dilut- 



VOL. VIII. NO. I JAN. 1828. K 



