Source : Webster's Revised Unabridged Dictionary (1913)

Photosynthesis \Pho`to*syn"the*sis\, n. (Plant Physiol.)
   The process of constructive metabolism by which carbohydrates
   are formed from water vapor and the carbon dioxide of the air
   in the chlorophyll-containing tissues of plants exposed to
   the action of light. It was formerly called {assimilation},
   but this is now commonly used as in animal physiology. The
   details of the process are not yet clearly known. Baeyer's
   theory is that the carbon dioxide is reduced to carbon
   monoxide, which, uniting with the hydrogen of the water in
   the cell, produces formaldehyde, the latter forming various
   sugars through polymerization. Vines suggests that the
   carbohydrates are secretion products of the chloroplasts,
   derived from decomposition of previously formed proteids. The
   food substances are usually quickly translocated, those that
   accumulate being changed to starch, which appears in the
   cells almost simultaneously with the sugars. The chloroplasts
   perform photosynthesis only in light and within a certain
   range of temperature, varying according to climate. This is
   the only way in which a plant is able to organize
   carbohydrates. All plants without a chlorophyll apparatus, as
   the fungi, must be parasitic or saprophytic. --
   {Pho`to*syn*thet"ic}, a. -- {Pho`to*syn*thet"ic*al*ly}, adv.