102 GERMINATION 



so the extent of the leaf surface increases ; while a diminished 

 water supply is met by a smaller leaf surface, admitting of 

 less transpiration." 



And also of a lower air intake. 



" Thus on moist soils — clays and loams — the plants 

 usually have large wide leaves and grow to a considerable 

 size, whilst on the drier sands the vegetation is narrow 

 leaved and more stunted." 



Due, in some measure at least, to lowered current supply. 



" A copious water supply leads to a more protracted 

 growth and to a retardation of the ripening process ; indeed, 

 in very wet districts grain crops are grown only with difficulty 

 if at all, because ripening may be so long delayed that frosts 

 supervene and damage the crops." 



Now copious water supply counterfeits electrical stimulus 

 by reducing soil resistance to the minimum permitted by 

 temperature and encourages the plants to continued growth. 

 I have mentioned elsewhere (p. 54) that under electrical 

 stimulus I had some Mustard Plants over four feet high, 

 but the seeds were few in number and very late. More 

 water is needed during the period of active growth than 

 during germination or ripening, but, as Dr. Russell observes, 

 " much more work is required from the physiological side 

 before definite rules can be laid down." 



We know, however, that in countries such as Egjrpt and 

 India, where higher temperatures prevail some plants 

 require a great deal of water, the supply of which is some- 

 times a matter of considerable difficulty. Cotton needs, 

 I believe, about thirty inches, and Rice not less than eighteen. 

 If I can show that some part of this supply can be dispensed 

 with it will not be without a practical bearing upon horti- 

 culture and agriculture. 



Some years ago I carried out a series of experiments with 

 ferrous sulphate as an electrolyte and gave an account of 

 one or two of them in Electro-Pathology and Studies in Electro- 

 Physiology. Since then other experiments have been made, 

 and as they confirmed the results previously obtained, 

 some mention of them may be useful at this juncture. 



