346 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
consideration of the causes which have been suggested to account 
for the facts. 
Light being necessary for the normal nutrition of green 
plants, it is not surprising that botanists should, as a rule, have 
looked at etiolation either as a simple case of starvation or 
more vaguely as a pathological condition produced by disturbed 
nutrition. 
Thus Kraus * held that where etiolated leaves remain small, 
it is due to the want of the formative material with which light 
would have supplied them. In one of his experiments he 
etiolated a vine shoot, and having covered one half of a dwarf 
leaf with opaque material, he allowed light to reach the rest of 
the plant. The result was that the illuminated half of the leaf 
developed chlorophyll and increased in size, while the darkened 
half remained small. 
The conclusions of Kraus were met by a research of 
Batalin's.t He exposed etiolated plants to faint light for an 
hour or two every two or three days, regulating the duration and 
degree of illumination so that no chlorophyll was formed. The 
result was that the partly lighted plants developed leaves several 
times as big as those which were continuously darkened. This 
shows plainly that the deformity of the completely etiolated 
plants was not due to the nutritive disturbance of darkness, and 
did not, in fact, depend on the absence of assimilation. 
This was also the conclusion of Vines,^ who starved his 
experimental plants, not by darkness, but by depriving them of 
CO2, so that, although exposed to light, they were unable to 
assimilate. 
Recent work § has, however, shown that interference with the 
chlorophyll-function has a remarkable effect on the leaves : not 
merely their growth, but their periodic movements — in fact, their 
life as a whole — depending on the presence of CO 2. These 
researches make it clear that the element of nutrition has ta 
be reckoned with to a greater extent than the above quoted 
experiments of Batalin would seem to show. The subject is 
♦ Pringshcim's JahrbUcher, 1809-70, vii. 
t ]JoL Zcitunq, 1871. 
X Arbeitend. hot. Tnslituis ill Wilrzhurcj, Bd. ii. 1878. Godlcwski's paper 
in thf! Bot. Zcituvg, 1879, p. 90, confirms this result. 
§ Vochting, L'o^. Zcitwifj, 1891, p. 113, and Jost, Pringshcim's Jalirhilchcry 
1895, p. 40:J. 
