PHOTOSYNTHESIS 85 
plant growing in the light in an atmosphere free from 
carbon dioxide cannot manufacture carbohydrates any 
more than if it were in the dark. A plant lacking chloro- 
plasts, e.g. the fungi, cannot manufacture carbohydrates 
from carbon dioxide even if light be present (excepting cer- 
tain bacteria, the so-called nitrite and nitrate bacteria). 
The process takes place in the chloroplasts apparently. 
The light rays most effective in photosynthesis seem to be 
those in the red part of the spectrum while those at the 
violet end also have some value. Those lying between 
seem in the main to be useless. The green color represents 
the portion of the white light that strikes the chlorophyll 
and is reflected back or passes through it without being 
absorbed. The raw materials are carbon dioxide and 
water, the energy is derived from the absorbed rays of 
light and the end products are carbohydrates and oxygen. 
125. The exact steps in photosynthesis are not 
certainly known but the following seems to be the 
probable course of events: 
CO.+ H.0 = H.COs; (water, plus carbon dioxide, equals 
carbonic acid). 
H.CO;=H.CO+0, (carbonic acid acted on by the 
energy derived from light by the cholorophyll is changed 
into formaldehyde and oxygen). 
_6H:CO=C.Hi20, (formaldehyde, probably by the 
_ gid of more energy derived from the light is polymerized 
into glucose). 
It will thus be seen that for every molecule of carbon 
dioxide used up one molecule of oxygen (Oz) will be set 
free. Glucose is the carbohydrate first formed in most 
cases but as this accumulates in the chloroplasts and 
cell sap it is often transformed rapidly into the insoluble 
starch (CsHioOs)n which becomes stored up in large 
quantities in the chloroplasts. Sometimes instead of 
