158 Miscellaneons. 



showing that the cause of this destruction must be the escape of gas 

 from the pipes. 



M. Ulex mentions several other localities where similar facts have 

 occurred, so that there can no longer be any doubt as to the injurious 

 influence of coal-gas upon vegetation. We must not, however, con- 

 clude from these circumstances that this is a necessary consequence 

 of the introduction of gas-lights. In Leipzig for instance, the gas- 

 pipes pass through the promenades without any appearance of injury 

 to the trees. This arises from the junction of the pipes being much 

 more carefully effected than at Hamburgh, so that escapes of gas are 

 much more rare. 



From these observations it follows, that it is as well to allow gas- 

 pipes to pass as far as possible from plantations of trees, and that wheu 

 this cannot be managed, great care must be taken to render the junc- 

 tions of the tubes as perfect as possible. — Journ. fur prakt. Chemie, 

 Ivi. p. 257. 



On the Habits of the Wigeon. By Matthew Moggridge. 

 To the Editors of the Annals of Natural History. 



The Willows, Swansea, Jan. 8, 1853. 

 Gentlemen, — Last summer a pair of wigeons were observed on 

 the lower lake at Penllergare, long after their brethren had migrated. 

 At last I saw them swimming about with five young ones, and 

 watched them vnth a good pocket-glass for some time at the distance 

 of about 100 yards. The keepers and some others saw them also, so 

 that there is no doubt of the fact. 



Your obedient servant, 



Matthew Moggridge. 



On the Relations between the Oxygen consumed by the Spadix of 

 Arum italicum and the Heat produced by it. By M. Garreau. 



The observations of M. Garreau confirm the well-known facts of 

 the augmentation of the heat of the spadix of Arum italicum at the 

 moment of flowering, and with redoubled intensity at certain hours, du- 

 ring several consecutive days. As might be expected, the oxygen taken 

 from the air to form carbonic acid gas, and the development of heat 

 are correlative phsenomena. M. Garreau has measured the oxygen 

 consumed at different hours ; the difference is considerable. Thus, 

 an Arum on the 7th of June indicated an increase of heat of 4°'5 Fahr. 

 at half-past three in the morning ; about half-past six the temperature 

 had risen to 16° Fahr. above that of the surrounding atmosphere, 

 and then diminished again to half-past nine. During this period of 

 six hours the spadix consumed say 341 volumes of oxygen, whilst in 

 the ensuing eighteen hours it only consumed 184. The same phse- 

 nomena took place during several days. 



•' It was interesting to ascertain," says M. Garreau, " whether 

 there existed any organic cause, by means of which the ready action 

 of atmospheric air upon the spadix of this Arum could be explained. 

 Microscopic examination shows, in fact, that it presents a much larger 

 absorbing surface than could have been supposed, as the cells forming 



