EXPOSURE ON LENGTH AND BREADTH OF LEAVES. 877 
cases I took care to keep to the lower and mature (though not 
withered) leaves, and I usually measured at least one hundred 
leaves of each form. The measurements are expressed in decimals 
ofaninch. The last column is the caleulated decimal value of 
the length divided by the breadth, which I have called the leaf- 
ratio. I have found this ratio of the greatest use in studying 
the effect of exposure. 
Table II. shows the result of the whole set of observations 
made on grass-leaves. 
Taste II. 
Leaf-proportion in Grasses. 
| | 
Length | Breadth | Leaf- kiss 4 
of leaf. | of leaf. | ratio. enint | 
measured. | 
RM | REE. 
| 
Stenotaphrum glabrum. Form A| 79 | %5 15:8 68 | 
35 3) Form B 182 | 3 6:07 60 | 
Paspalum distichum, L. Form A| 23 | «I 23 60 
T a Form B| 11 Ai 11 60 
Cynodon Dactylon, Pers. Form A T3 1 73 100 
” e Form B 45 1 45 60 
Eragrostis ciliaris, Link. Form A 3-24 T 32:4 53 
v 2 Form B 28 | :16 17:5 38 | 
| Cenchrus echinatus, L. Form A 832 | 37 | 25 60 | 
| re 2 Form B 455 | 23 | 198 90 | 
| Centotheca mucronata, Hack. ...... 2:89 43 | 67 80 | 
| Centotheca madagascariensis Hack. 54 «47 | 11:5 100 | 
| ZAuarea sarmentosa, Pers. ........- 81 xi 27 100 
| Eragrostis plumosa, Link ............ 1:94 :13 | 15 100 
It is seen that there is no exception in the first five cases to 
the rule that in Form A, which is that from sheltered ground, 
the leaf-ratio is the greatest, or the leaves are relatively longer. 
The two Centothecas are very interesting, as I took them to be the 
Same species, and the second (C. madagascariensis), corresponding 
to Form A, was from more sheltered places than the other. 
This tends to show how specific differences may arise (see infra). 
Thuarea is a prostrate grass which grows in sandy soil, and con- 
trasts strongly with Eragrostis plumosa, which is an upright shade- 
form. The next series were made from such plants as I could 
collect in a short distance from my house, as I was disabled 
through fever and other ailments from walking far at the time. 
(Table III.) 
It is seen that in the whole set of fifteen species there are 
2 12 
