PART II.—EXPERIENCE IN OPEN AIR OR NATURAL CLIMATE. 
Chapter X. 
STUDIES IN PHENOLOGY. 
Under the general heading we shall consider, first, the wild plants 
and their natural habits; second, the plants cultivated at experi- 
ment stations under instructive experimental conditions, and, third, 
the statistics of each and the experience of farmers in general from 
a practical point of view. The study of the forest or natural habits 
of plants leads us into the phenology of plant life. 
Phenology is a term first apphed by Ch. Morren to that branch of 
science which studies the periodic phenomena in the vegetable and 
animal world in so far as they depend upon the climate of any 
locality. Among the prominent students of this subject, one of the 
most minute observers was Karl Fritsch, of Austria, who in his In- 
structions (1859) gives some account of the literature of similar 
works up to that date. He distinguishes the following epochs in the 
lives of plants, and especially recommends the observation of peren- 
nial or forest trees that have remained undisturbed for at least sev- 
eral years. His epochs are: 
(1) The first flower. 
(2) The first ripe fruit. 
The next important are, for the annuals: 
(3) The date of sowing. 
(4) The date of first visible sprouting. 
In order to assure greater precision he adds: 
(5) The first formation of spikes or ears. 
As Fritsch considers that the development of the plant so far as 
its vegetative process is concerned depends principally upon tempera- 
ture and moisture, but that its reproductive process depends prin- 
cipally upon the influence of direct sunlight, therefore he adds a 
sixth epoch for trees and shrubs—viz : 
(6) The first unfolding of the leaf or the leaf bud or frondescence. 
This is the epoch when by the swelling of the buds a bright zone 
is recognized which opens out and the green leaf issues forth. Cor- 
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