80 
i. e., short waves, had access to the tubers. Vochting finds that, 
although the light does delay the growth and diminishes the distance 
between the tubers, still the supply of water is the important factor. 
(Wollny, X, p. 230.) 
Sachs (1887), as the result of experiments on the effect of ultra- 
violet radiation upon the formation of buds, states that these rays 
exert on the green leaves (in addition to the assimilation produced 
by the yellow and neighboring rays) still another effect that consists 
in the development of particles that contribute to the formation of 
blossoms. These bud-forming particles move from the leaves into 
those parts of the plant where they are to bring about their own 
development into buds. We therefore now know of three different 
portions of the solar spectrum having very different physiologicai 
influences: The yellow and neighboring rays, which bring about the 
transformation of carbonic acid or the formation of starch; the blue 
and visible violet, that act as stimulants to motion; the ultraviolet 
rays, that produce in the green leaves the material for the formation 
of buds. (Wollny, X, p. 230.) 
INFLUENCE OF DRYNESS AND SUNLIGHT ON DEVELOPMENT 
OF TUBERS. 
In the climate of Germany the flowering of different varieties of 
potatoes is very much restricted. Only a small number of varieties 
flower regularly and bear fruit, whereas in Chile the plant flowers 
abundantly, but the tubers are small; in other words, in the Tem- 
perate Zone the formation of tubers is favored at the expense of 
fertilization; the energy of the one process increases while the other 
diminishes. 
Knight and Langenthal have found that by detaching the young 
tubers they increase the blooming, and on the other hand, by cutting 
off the flowers they increase the development of the tubers, thereby 
largely increasing the harvest. Wollny, in 1886, experimented on 
four plats, each for many varieties of potatoes. He found that cut- 
ting off the flowers increased the crop of tubers as to number, 
size, and weight, but that something depended upon the time of 
cropping the flowers, which is best done a considerable time before 
they arrive at maturity. It seems probable that dryness and sun- 
light stimulate the formation of flowers, but humidity and cloudi- 
ness, at least up to a certain limit, stimulate the formation of tubers. 
This harmonizes with some recent results obtained by Sachs, who has 
shown that the ultraviolet rays stimulate the flowering. (Agr. Sci., 
Vols p.c2(3.) 
