Chap. I. INTRODUCTORY REMA.RKS. 13 



kinds of seeds would not germinate well when exposed 

 to the light ; though the glasses containing them were 

 kept on the chimney-piece on one side of a room, 

 and some way from the two windows which faced 

 the N.E.* 



, The soil in the pots in which the seedlings were 

 planted, or the seeds sown, was well mixed, so as to 

 be uniform in composition. The plants on the two 

 sides were always watered at the same time and as 

 equally as possible ; and even if this had not been 

 done, the water would have spread almost equally to 

 both sides, as the pots were not large. The crossed 

 and self-fertilised plants were separated by a super- 

 ficial partition, which was always kept directed towards 

 the chief source of the light, so that the plants on both 

 sides were equally illuminated. I do not believe it 

 possible that two sets of plants could have been sub- 

 jected to more closely similar conditions, than were 

 my crossed and self-fertilised seedlings, as grown in 

 the above described manner. 



In comparing the two sets, the eye alone was never 

 trusted. Generally the height of every plant on both 

 sides was carefully measured, often more than once, 

 viz., whilst young, sometimes again when older, and 

 finally when fully or almost fully grown. But in 

 some cases, which are always specified, owing to the 

 want of time, only one or two of the tallest plants on 

 each side were measured. This plan, which is not a 

 good one, was never followed (except with the crowded 



* This occurred in the plainest species germinated on the hare 



manner with the seeds of Papaver sand, though left there for some 



varjum and Delphinium consolida, weeks; but when these same seeds 



and less plainly with those of were placed on earth in pots, and 



Adonis xstivalis and Ononis minu- covered with a thin layer of sand, 



titsima. Rarely more than one they germinated immediately in 



or two of the seeds of these four large numbers. 



