DAA PRINCIPLES OF BOTANY, ETC. 
which ‘soils. Microscopical examination has shewn, 
that this rust-like matter consists of small fungi, 
which are called Aecidium, and the seeds:of which 
form this brownish powder. We find them fre- 
quently inithe leaves and stems of Euphorbia Cy- 
parissias ; Berberis vulgaris ; Rhamnus catharticus ; 
and some gramina; of wheat, oats, &c. If they are 
very numerous, especially in the different: species of 
gramina and corn, consumption is the consequence. 
» Little 1s to be done against this affection. In the 
species of iwheat, oat, and the like, some have re- 
commended to moisten the grain, before sawn, in 
salt, or lume water, or to sow grain from countries 
where this disease does not prevail. Palliatives, «ar 
preservative means, are of no use. . | 
§ 13139. 
Lepra.is frequently met with on the trunks, espe- 
cially of young trees. If trunks are so entirely 
covered with algae, that the pores of the cutis be; 
come shut up, we call the distemper /epra. » Old 
trees have their trunks full of algae, without suffer- 
‘ing in the least, provided the smaller branches be 
free of them. But if young trees or shrubs grow in 
too sterile a soil, or in too thin a stratum of fertile 
soil, or in gravelly soil; im improper situations, the 
ground being either too moist or too dry,’ and the 
plants, against their nature, too much exposed to 
wind; then they sicken, their bark cannot perform 
with proper vigour the functions peculiar to it as the 
skin-of the tree, and they grow at last, even at their 
yous boughs, all over with fungi of all kinds. : .,Vi- 
| gorous 
