266 IS SILICA A CONSTITUENT OF PLANT FOOD? 



solution on June 8th, while number 3 was put in on the following 

 day. 



The water culture solution was made up as follows : — 



In 1 litre of distilled water was dissolved 



1 gramme of Calcic Nitrate 

 .25 „ „ Potassic Nitrate 



.25 „ „ Magnesic Sulphate 



.25 ,. „ Dihydric Potassic Phosphate 



.25 „ ,, Ferric Phosphate. 



By kind permission of Dr. Hahn these experiments were 

 carried out in his greenhouse, where the plants were safely pro- 

 tected from the strong winds. On calm days they were put 

 outside and exposed to the direct rays of sunlight. 



The rate at which these young plants grew in the solution 

 was very striking, no indication being given that they were 

 sacrificing their health for height. It may be interesting here 

 to give the measurements of these young plants during the first 

 few days of growth in the water culture solution to illustrate 

 this rapid growth. 



June 12th. 13th. 14th. 15th. 16th. 17th. 23rd. 



No. 1 4f" 54" 6V 7\" 8i" 8$" taj" 



No. 2 4$" S" 6" 7*" 8 ; ' 8{" 12}" 



No. 3 2\" 2f" 3 r 4!" 5i" 51" to" 



The solutions had to be filled up every day with distilled 

 water, owing to the transpiration current through the plant of 

 water which enters by the root hairs, and is eventually evapo- 

 rated from the leaves and other growing surfaces of the plant. 

 This amount became considerable when the plant became full 

 grown. On a warm day as much as 500 c.c. was observed to 

 be the decrease in volume of the culture solution. The solutions 

 in which the young plants were growing were frequently shaken 

 up so that more air, and hence oxygen could be dissolved. 



On July 12th, August 26th, September 9th, September 29th, 

 October 12th, fresh water culture solution was put in. These 

 growing plants were carefully watched, and if at any time a 

 fungus was noticed on the cork or cotton wool these would be 

 immediately replaced by fresh sterilized material. 



The height to which these plants grew and the enormous 

 number of stems and leaves produced in each case were very 

 striking; in fact they looked more like bushes, and gave one the 

 impression that they were making full use of the food material 

 supplied, and were not sparing themselves in any way. 



The plants, having come to perfection, were on October 20th 

 removed from the solutions and hung up to dry. The heights 

 thev attained were as follows : — 



