Sunrise and Growth. 253 



which might easily have been attributed to the seed or to the soil 

 had not records been kept of the amount of sunrise rays each plant 

 had received. It was quite certain 



1°. That wherever plants had received a greater share of 



the earliest rays than their neighbours, even though the distance 



between them might be only four inches, they had grown more 



rapidly. 

 In consequence of a difference of 18 minutes between the times the 

 south and north ends of Rows I. and II. received direct sunlight, 

 there was a marked difference between the peas there. There were 

 four strongly-defined lines stretching diagonally across the rows, 

 where growth had been stimulated by early rays which came through 

 gaps between distant trees and out-houses, or through crevices in 

 the hedge. Though the rays passed to the adjoining plants in less 

 than 10 minutes, the latter were inferior, and never grew to as large 

 a size. 



2°. That rays which fell on ground after 8h. 43m. did not 



have the same effect upon growth as those previous to that 



hour. 



Sunrise was at 6.25 a.m. about this time. Up to March 23rd 

 no seed had germinated at the north ends of the rows, within the 

 shadow cast by the hedge up to 8h. 43m. There was no exception 

 to this, and the line of shadow at that hour could be distinctly traced 

 by the line of growth. 



The first result can most easily be explained by considering it as 

 an effect of temperature, though it is remarkable that the loss of only 

 10 minutes of direct sunlight at this hour of the day should have 

 caused such a marked difference in the growth of plants which were 

 not more than three inches out of the line of the ray. We cannot, 

 however, leave out of account the action of light in arranging chloro- 

 phyll-granules on cell-walls according as it is diffused or direct, nor 

 the fact that the chloroplasts are most active when illuminated by the 

 red, oninge, and yellow rays of the spectrum. 



Differences of temperature, however, will not explain the second 

 result. Here the direct sunlight from 8h. 43m. to nearly i6h. was 

 powerless to make the end seeds in 14 rows out of 26 germinate. But 

 when, owing to the sun's increasing northerly declination, direct light 

 came through a gap about yh. 15m. and fell on the same portion of 

 these rows, the seeds put up leaves. This occurred in numerous cases 

 after March 23rd, and there could be no mistake about the observa- 

 tion. 



With the view of obtaining further information regarding these 

 two results, and of determining whether plants which were deprived 

 of the sunrise rays up to 8h. 43m. would show any etiolation, or 

 decreased action on the part of the chloroplasts, the following experi- 

 ment was made. 



On March 22nd a portion of Rows I. and II., in which the peas 

 had received the same amount of the earliest rays, and were particu- 

 larly strong and even in growth, was shaded off by an iron screen 2ft. 

 4ins. long and 9 inches high. It was fixed in the ground 7 inches 



