DISEASES OF PLANTS, 369 
pidity.as before. Improper soil often favours sterility. 
If succulent plants, for instance, Cactus, Mesem- 
byanthemum, be placed in rich garden earth, they 
may grow in it, but scarcely ever, at least very 
rarely, bear blossoms. Are they, however, placed 
ina ground mixed of loam and sand, then they 
will easily shew their blossoms, if they are rightly 
treated. [ll treatment indeed suppresses in many 2 
plant the approaching flower. Amaryllis formosissi- 
ma, if kept constantly in pots, filled with garden- 
earth, produces many leaves, but no flowers. But, 
if its bulb be taken out and preserved in a dry place, 
out of ground, during the winter, a flower will ap- 
pear every year. Many other bulbous plants, which 
grow in sandy plains in warm climates, do the same. 
Instances would be superfluous. 
§ 345. 
Abortus. If flowering plants, which are provided 
with perfect female organs of generation, do not 
bear fruit, abortion has taken place. ‘This depends 
on a want of male organs of generation, or a vi-_ 
tiated structure of the separts, violent storms, on va- 
rious disorders, too great age and too much sap, 
Every botanic garden can shew us numberless in- 
stances of abortion. How often do we lose exotic 
plants, bearing no seeds, because the male organs 
are either wanting or in an imperfect state! How 
often might insects, could we obtain proper species, 
do this office! If there 1s not sufficient warmth, 
which is so often required, to ripen a foreign fruit, 
this must necessarily drop off in its immature state. 
| Aa Drought 
