LIMITS OF ENDURANCE OF DIFFERENT FARM CROPS. 199 



the possibility of this ingredient being present in other 

 substances which are used commercially. 



Amongst these must be counted fertilisers compounded 

 of superphosphate in the preparation of which sulphuric 

 acid is employed. If the ingredients employed in the manu- 

 facture of the acid are not free from arsenic, this substance 

 will be present in the resulting fertiliser. It is known to 

 have an injurious effect upon the growth of plants, and the 

 following experiments will indicate its effect upon wheat. 



The following pots were sown on June 3rd in No. 1 soil, 

 the complete fertiliser having been added, together with 

 varying amounts of arsenic trioxide: 



Pot 37, # 01 per cent. As,0 3 

 „ 38, -05 

 „ 39, -10 

 h 40, -50 

 „ 41, 1-00 



Pot 37, germinated well, plants not affected and growing 

 well on July 1st and 24th, and were growing well on 

 August 26th; grain is now forming in the ear Oct. 8th. 



Pot 38, germinated well, but early growth not very vigor- 

 ous, plants growing fairly August 26th ; grain is in the 

 ear on October 8th. 



Pot 39, germinated fairly well and plants growing fairly 

 on July 1st, subsequent growth poor and weak. Oct. 

 8th grain is forming in the ear, but plants are very 

 stunted and grain backward. 



Pot 40, germination poor, plants very puny (July 1st), and 

 almost dead by July 24th, still alive but very feeble 

 by Aug. 26th, all dead by October 8th. 



Pot 41, germination and early growth very feeble, plants 

 nearly dead by July 24th, all dead by August 26th. 



The conclusions drawn are as follows : — germination and 

 early growth is affected by the presence of *05 per cent. 



