DISEASES OF PLANTS. 355 
dry. Late night frosts, severe cold in winter, burn- 
ing heat, corruption of the sap in single branches, 
and smaller plants, are its causes. _ : 
Frost coming on ata late period in spring, very 
frequently kills young shoots of plants, which there- 
fore grow black, and shrink up. To obviate this 
accident, young plants should be covered as soon as 
cold nights may be dreaded. Others derive great 
advantage from conductors of frost, as they style 
them, that is, from a compactly twisted cord of 
straw, directed into a vessel with water. From se- 
vere winter cold, foreign trees suffer chiefly, and such 
of our native plants as are very delicate. ‘Their 
inner bark becomes frost-bitten, turns black, and it 
is impossible to save them. The whole must be 
clipped, and the main trunk with the roots only be 
allowed to remain, to produce new shoots. Intense 
heat will produce ‘the same bad effects in gardens, 
or even in forests, where forresters are permitted to 
clear away the mosses and dry leaves from the roots. 
Single branches sometimes, by the too rapid growth 
of others, are deprived of their necessary food, they 
become dry and fall off. This may happen without 
any injury to the whole. Smaller plants sometimes 
induce’ this disease, most frequently in the bulbs of 
the saffron, where a species of Lycoperdon oc- 
casions it. One part of the coast of Africa, the 
gold coast, is infested by ‘a wind called Harmattan, 
which kills the a ae their leaves dry and 
black. | 
Z2 § 330. 
