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ABNORMAL VITAL PHENOMENA AND CONSEQUENT = 
ABNORMAL DEVELOPMENTS. | | Ree 
_ That section of botany which treats of the abnormal 
vital phenomena and the consequent abnormal developments  — 
of plants, is called Vegetable Pathology; and may be divided. 
into two subdivisions, 7eratology or the study of malforma- 
- tions, and /Voso/ogy or the diseases of plants. ‘The formeris 
concerned with deviations from ordinary structure in the ae . , 
organs of the plant, the latter with variations in the vital | ay 
functions. ‘This whole subject, therefore, independently of ‘a 
its practical importance, is also of great scientific interest, 
the former part especially in relation to morphology, the 
latter to ‘physiology. It is, however, impossible to draw 
any sharp line of demarcation between malformation and . 
disease, and often one cannot be conceived mito the 
other. 
The causes of the phenomena now under consideration 
he in a want of conformity of the plant, partly to the con- 
ditions of its environment, partly to those of other plants, 
and partly also in injuries inflicted by animals. In a cer- 
tain sense also, treatment by man may be a source of ab- 
normal vital phenomena; inasmuch as he prescribes the 
conditions in which the plant shall grow. Most cultivated 
plants live in conditions which were foreign to their uncul- 
tivated ancestors, and they have frequently undergone such 
change that their parentage cannot be recognised.  It.is, 
indeed, often the object of cultivation to cause such devia- 
tions. Thus, the brussels-sprout is cultivated on account 
of the monstrous edible thickening of the stem, and the 
cauliflower on account of its peculiarly metamorphosed in- 1 
florescence. A very high cultivation produces, however. other 
modifications besides those aimed at and less desirable in ‘ of 
themselves. ‘Thus, there is no doubt that the cultivation of 
- fruit-trees has resulted in an enfeeblement of their vege 
