24:2 PRINCIPLES OF BOTANY, ETC. 
§ 238. 
Some oi the vessels now described conyey the sap 
which differs in its nature in different species of 
piants: It is 
Resinous, in the different species of fir, &c. 
Gummy, in fruit-trees and some species of Mi- 
mosa, 
Lymphatic, in almost all plants. 
Sap likewise varies in colour: It is 
White, in Euphorbia, Papaver, Leontodon, Pi- 
nus, &c. 
Yellow, in Chelidonium. 
Red, in Rumex sanguineus, Dracaena draco, Ptero- 
arpus santalinus, Calamus Rotang. 
Blue, in the root of Pimpinella nigras 
Green, in S0me umbellatae. 
Colourless in most plants. 
The sap in fruits, we know, is of various 
tinges. Rafn discovered a great analogy between the 
sap of plants and the blood of animals. He detected, 
with a microscope magnifying 35 times, in the lymph 
of Euphorbia palustris, round globules, like those 
in blood, which swam in a fluid which was clear, but 
not so clear as water. ‘The same I observed myself 
in the sap of the Rhus towxicodendron. Rafn, how- 
ever, found in the Euphorbia, besides the glo- 
bules, prisms, which he likewise saw in Euphorbia 
peplus, helioscopia, esula, cyparissias, and lathyris, 
though they differed somewhat. In no plant but the 
Euphorbia and Hura crepitans he could detect the 
| prisms. 
