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CULTIVATION OF PLANTS. 
LECTURE XLII. 
Plants as affected by cultivation. 
You may recollect that we have before remarked, upon the 
permanence of species, and have observed that although they 
may in some respects be varied by cultivation, yet their distinct- 
ive characters will not be wholly lost. The differences which 
exist in species are expressed by the terms, races, varieties, and 
variations. , 
Races are those differences in a species which are of a strik- 
ing kind, and continued from the parent plant to its offspring 
by being propagated by the seed. They are produced by strew- 
ing pollen of one species upon the pistils of another ; the seed 
thus formed will produce a plant resembling both. 
Varieties are a less important distinction than races; they 
are not continued by means of the seed, but produced by graft- 
ing or continuation of the plant under some new circum- 
stances. 
Variations . denote the slightest kinds of difference ; they are 
occasioned by peculiarities of climate, soil, moisture, dryness 
&c. All these terms, races, varieties and variations are often 
used indiscriminately for each other. 
Degeneration or change of the organs of plants. 
The organs of plants owing to peculiar causes, often experi- 
ence a metamorphosis, and instead of their usual appearance 
exhibit anomalies or vegetable deformities. 
We use here the term deformity, as signifying any variation 
from the ordinary course of nature. The causes which produce 
these changes are, 
1st. The adhesion of parts usually separate; thus we often 
see flowers, leaves and fruits united, and appearing double. 
Some writers, among whom is the celebrated French botanist, 
De Candolle, assert that the single petal which forms the corol- 
la of many flowers as the stramonium or the blue bell, is in 
reality composed of several petals which become soldered, or 
cohere together before the flower expands. The same writers 
consider a monophyllous calyx, to be in reality composed of 
several little leaves thus united before their developement. 
Plants affected by cultivation — Permanence of species — Races — Varie- 
ties — Variations — Changes of the organs of plants — Deformities. — 
