348 - PRINCIPLES OF BOTANY, ETC. 
bud. - From this a fleshy’ mass of the size of a 
fist arises, covered all over with hair-like coloured 
processes. 
/§ 319. 
‘Chlorosis is that affection of plants, when their 
green colour €éntirely disappears, and all their parts 
grow whitish. It arises‘fromi this circumstance, that 
these plants cannot excrete their oxygen, which 
therefore becomés accumulated. There are three 
causes of the disease, want of light ; insects; and 
bad soil. We saw before, (§ 278), that a healthy 
plant emits oxygen gas in sun light, and that the ac- 
cumulation of this gas, when’ not emitted, makes the 
sreen colour disappear, (§ 281).” 
“As soon as a plant/is deprived of light, it cannot 
disengage the oxygen, hence it assumes a white co- 
lour, which however instantly ‘goes off, when the 
rays of the sun are again admitted. ‘This is the rea- 
son why plants, in dark rooms, between’ great masses 
of ‘stone, in deep clefts of rocks, beneath the dark 
shade of shrubs and trees, &c. grow ae and.of a 
whitish colour. | HELD 
Insects which bite oi the radicles of slate se or 
even nestle'in them, and consume they food, debi- 
litate: their vessels, render them insensible of. the 
stimulus of light, and at last chlorotic. It occurs 
very frequi ently in Secaleicereale. No remedies are 
ef any use. 
Improper soil, from which plants do not get food 
enough, not unfrequently brings on this affection. 
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