Development of Chlorophyll. 809 
obtained quite contrary results to those here arrived at, and he concludes 
that C 0 2 somehow is concerned in the development of chlorophyll from 
etiolin, because he finds that less C 0 2 escapes during illumination in the 
early stages of greening than in a period of darkness. The differences that 
he observed were not great and not always in the same direction, but it is 
not easy to explain the general lack of agreement with the present work, 
especially as Wiesner also used Barley seedlings. 
In order to examine this question more critically similar experiments 
were made with cut tips of etiolated 
shoots of Vicia Fab a and with cut 
etiolated leaves of Barley, exposed to 
a constant artificial light. In cut shoots 
there is no longer the respiration of 
roots, seeds, and colourless parts to be 
contended with, and the faintest be¬ 
ginnings of photosynthesis should be 
easily detected. 
The cut shoots were placed in a 
different type of chamber, shown in 
Fig. 4, 1 which has a much smaller 
internal volume. It is of the same 
pattern as the chambers described by 
Blackman and Matthaei in the fourth 
paper of this series. The air current 
enters at D and leaves at E, having 
passed through a calcium chloride 
tube, G, to prevent the water evaporated 
from the wet chamber being subse¬ 
quently deposited and blocking the 
tubes. Tube F is for supplying water. 
The chamber is supported ver¬ 
tically on a brass stand and is sub¬ 
merged in a large cubical copper bath kept at a constant temperature. 
On the side of the bath in front of the chamber is a large glass window, 
through which the etiolated shoots can be illuminated by a pair of Keith 
high-pressure incandescent gas-burners, kept at a standard distance from 
the chamber. 
A continuous current of air freed from C 0 2 is sucked by an aspirator 
through the submerged chamber. On leaving at E it passes to a set of 
parallel Pettenkofer tubes each containing a known quantity of standard 
1 The etiolated bean shoots shown in the figure are held lightly in position by pressure between 
the glass front and the glass back of the chamber. 
