in vegetable Structures. 



245 



acid gas, as well as the formation of free acetic acid ; which 

 may be readily proved, by allowing seeds to germinate in 

 moistened protoxide of lead. The acid developed combines 

 with the oxide, forming acetate of lead, which, by digestion 

 in water, may be dissolved and crystallised ; the crystals thus 

 obtained evolving a pungent odour of acetic acid on the 

 addition of a little sulphuric acid* In consequence of this 

 formation of acetic acid, litmus paper, on which seeds are 

 allowed to germinate, becomes red ; a fact shown to hold good 

 with many kinds of seeds by Becquerel, to whom we are 

 indebted for an extensive series of observations on this subject, 

 of such physiological interest, that I need scarcely offer an 

 apology for transcribing a tabular view of the results obtained 

 by allowing different seeds to germinate on moistened blue 

 litmus paper.* 



Natural Order. 



Species of Plant. 



Action of the germinating Seeds on Litmus Paper. 



Graminaceae 



Legumindsae 



Cruciferae - 



Cichoraceae 

 Umbelliferae 



Pinaceae 



Cucurbit aceae 

 Linaceas 



LiUaceae 



Wheat 



Rye - . 



Barley 



Oats - 



E'rvum Lens 

 Peas - 

 Beans - 

 Sweet pea - 



Clover 

 l Lucerne 



" Sinapis alba 

 Sin apis nigra 

 Garden cress 

 Turnip 

 Cabbage 

 Wallflower 

 Lettuce 



f Carrot 



\ Parsley 



f Two species 

 ofPinus - 

 Melon - - 

 Linseed 



("Leek - 

 \ Onion - 



Assumes a red tint in an hour, becom- 

 ing very distinct in 12 hours. 



Effect distinct, but less decided. 



Effect intermediate between that of 

 wheat and rye. 



Effect similar to that of rye. 



Did not tint the litmus 

 paper red until after an 

 interval of 90 hours. 



The litmus paper became 

 red almost immedi- 

 ately. 



Action very 

 distinct. 



The litmus paper became red very 

 quickly, and in 12 hours the develope- 

 ment of acid was very decided. 



Production of the red tint very decided. 

 A feeble evolution of acid in about 24- 

 hours. 



Very intense action on the litmus. 



Distinct reddening. 

 Distinct reddening. 

 No action on litmus until after a lapse 



of 4 days, when reddening com- 



mencedi 



Having thus learned that, during germination, the supply of 

 starch in the albumen or cotyledons is replaced by sugar, and 

 crabonic and acetic acids, let us endeavour to ascertain how 



* Traite de l'E'lectricite et du Magnetisme, torn. iv. p. 

 t 3 



186. 



