308 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



E. — Experiments made in 1914. 



7. Series la. — Experiments in Pots with Ordinary Loam under Glass. 

 The plants chosen for this experiment were Primula malacoides, 

 Begonia semper ftorens, Eupatorium adenopkorum, and tomato. 



Primula malacoides. — A series of cultures was started with this 

 plant, but it soon became evident that there was great individual 

 variation between the plants in their characters and especially in 

 their rates of growth. Further consideration of this set was therefore 

 abandoned. 



Begonia semperflorens. — A series of seedling plants of this species 

 of equal size and age, and from the same batch of seedlings, was taken. 

 They were potted as follows : — 



No. of Plants. 



Compost. 



Loam. 



Bacterized Peat. 



Raw Peat. 





Parts. 



Parts. 



Parts. 



4 



7/8 



1/8 





4 



3/4 



1/4 





4 



1/2 



1/2 





4 



1 







4 



3/4 





I?4 



A considerable difference was to be seen between the plants within 

 a week or ten days of potting, and this difference became more marked 

 as time passed. The larger quantities of peat had, however, little 

 more effect than the smaller, while the only noticeable difference 

 between the set in ordinary loam and that in loam and raw peat was 

 a tendency in the latter to burn at the leaf margins. The plants 

 in loam and bacterized peat were all of a much deeper green, had 

 larger leaves, became considerably taller, and showed a much greater 

 tendency to branch from the base than the control plants. 



Eupatorium adenophorum. — A series of seedlings of this plant of 

 equal size and age was potted up on the same day (January 12) and in 

 similar composts to the foregoing. This is a particularly good plant for 

 such experiments, as it is remarkably uniform in growth, and grows 

 quickly, at the dull season of the year, in an ordinary greenhouse. The 

 four plants in each set were very uniform in their behaviour, and all 

 those in soil to which bacterized peat had been added grew consider- 

 ably taller than those in loam, were darker green in the foliage except 

 at the margins of the leaves which were of a lighter shade, more suc- 

 culent looking, and much more copiously branched. Those in the 

 compost of raw peat and lo?m were somewhat taller than those in 

 the loam alone, and showed in a much slighter degree the same 

 characters as those just referred to. The luxuriance of growth of 

 those in the treated peat compost was very marked. Measurements 

 were made of the leaves of all the plants on February 19, before there 



