V. The Inlluence of Light upon the Growth of Leaves. 
129 
Aclual numbers 
Percentages 
Before 10 
10—2 
After 
2 a. m. 
Before 
t 0 p. m. 
10—2 
After 
2 a. m. 
Secale 
6 
54 
15 
8 
72 
20 
Allinm 
2 
7 
1 
20 
70 
10 
Before 
9 p. m. 
9—3 
After 
3 a. m. 
Before 
9 p. m. 
9—3 
After 
3 a. m. 
Triticum 
— 
8 
— 
— 
100 
— 
Atliurn 
— 
3 
5 
— 
37.5 
62.5 
Before 
10 p. m. 
10—2 
After 
2 a. m. 
Before 
10 p. m. 
10—2 
After 
2 a. m. 
Cucurbita 
8 
to 
— 
44 
56 
— 
Totais. 
Before 9 p.m. 
9—3 
After 2 a. m. 
- 10 - 
10—2 
- 3 - 
Monocotyledons 
8 
• 72 
21 
Dicotyledons 
8 
10 
— 
Ihese figures shew thatj wilh regard to Monocotyledons, the occurrence 
of the maximum outside the nssigned limits took place in ahout 47 per ccnl 
of the ohservalions, and that of the minimum in aboul 29 per cent. 
With regard to Dicotyledons, the occurrence of the maximum outside the 
assigned limits took place in about 89 per cent of the observations, and 
that of the minimum in about 44 per'cent. 
Although in this analysis the ulmost lalitude has been allowed, yel 
the figures do not justify the significance which has been altachcd to them. 
The only indication that they give is, that the maximum of growth is 
attained, on the whole, somewhat earlier by Dicotyledonous tban by Mo- 
nocotyledonous plants. In order to account for this difference, Steblkr 
suggests that it is due to the retarding action of light. He says that the 
daily periodicity observed in the growth of the leaves of the former 
group of plants is a function of assimilalion modified by the retarding 
Arbeiten a. <1. bot. Institut in Würzburg. Bd. II. 9 
