380 MR. G. F. SCOTT ELLIOT ON THE EFFECT OF 
1887, p. 339) were an attempt to show that sunlight increased 
the size of the leaf. In the course of them he took measure- 
ments of the leaves of two sun-flowers, of which one was planted 
in the shade and the other in the sun. 
He did not, however, see any importance in the relation of 
length to breadth, and I have calculated the ratios in the third 
column of the following Table (V.). 
TABLE V. 
Dufour's experiments. 
Length in | Breadth in Leaf-ratio. 
mm. mm. 
| en 
| Ath leai SUN 500 86 24 ae 
| 5 shade 200 66 18 We 
me. 92 2D 2 
| ss shade 2.2... 40 11 A 
Gtm leafs aun ZI wv 102 25 Lo 
P Shader... 34 9 37 
Ftbleaftsuin: 600 | TIS 25 452 
E NM. dC uoces bo Z 8 425 
Sth leaf, sun « — 9. S | 121 Sl 3 A 
n o ade uu svo 47 11 42 
JEB leaf nsun ee | 140 38 3:68 
på shades 1 | 58 14 414 
General averages sun-leaves... 109 | 28 39 
Do., shade-leaves ............ | 465 | 118 | 3:95 
The slight confirmation is the more valuable, as Dufour had 
no idea of this relative difference. 
Sorauer, in a paper published in Wollny’s * Forschungen,’ 
Bd. ix., gives a number of tables which show exactly the same 
thing. In this paper he also points out clearly that in plants 
growing in wet air the leaves become longer relatively as well as 
actually. In the Botan. Zeit. 187 8, p. 1, a few more measure- 
ments are given by Sorauer, from which I extract the following, 
and have calculated the ratios :— 
Plants of dry air (average from five plants) gave for length of 
leaf 21:89 cm., for breadth 6:46 cm, or a ratio of 3:39. Similar 
plants grown in wet air gave for length 22:39, breadth 5'81, or 
a ratio of 3:85. Another set gave:—for dry air (average of nine 
plants), length 17-7, breadth 7:33, or a ratio of 2741; for me 
air (average of eight plants), length 17:9, breadth 674, i.e. à 
