176 BOTANICAL GAZETTE [SEPTEMBER 
the experiment which follows would indicate that the products 
- of photosyntax are not necessary to call forth the production of 
a leafy shoot. 
In order to determine whether the products of photosyntax 
as obtained from the use of the free CO, of the atmosphere are 
necessary to call forth bud production, a culture of leaves was 
made in CO,-free air in an apparatus similar to that figured by 
Pfeffer.2x At the end of three weeks the leaves showed a very 
abundant production of buds. It has long been known that 
plants are able to use the CO, of respiration as material for 
photosyntax. Since this is so, the above experiment does not 
prove conclusively that light is necessary to effect physical or 
chemical changes in material already present, for on account of 
the size of the Mnium leaf, the CO, produced by destructive 
metabolism would be considerable, and a small amount of car- 
bohydrate food might be formed. Later experiments with other 
species tend to show that it is the accessible supply of plastic 
material upon which the production of buds is dependent, and 
not upon physical or chemical changes in the material already 
at hand. 
Experiments with leaves in colored light by the use of 
double-walled bell-glasses filled with the solutions of potassium 
bichromate and ammoniated copper oxide, showed the produc- 
tion of buds as well in the strongly refrangible rays as in the 
less refrangible. The photosyntax would be greatly suppressed 
in the leaves exposed to the blue end of the spectrum, and thus 
this result points to a chemical or physical change in material 
already at hand. Since Klebs” has pointed out a difference in 
the relation of spore protonemata and leaf protonemata to light 
in a specific case, we might reasonably expect to find a differ- 
ence in the leaf productions from different species. Another 
point which may be noted in the case of the cultures in the rays 
of different refrangibility is that, in both the strongly refrangible 
and less refrangible rays, the leaves produced a much greater 
** Pflanzenphysiologie 1 : I91. 1881. 
22 Biologisches Centralblatt 13 : 646-648. 1893. 
