OUTGO OF THE PLANT. 149 



thus be easily transported to all parts of the plant. Wherever 

 there is need for new protoplasm, whether to repair previous 

 waste or to supply materials for growth, after absorption into 

 the cells the elements of the starch (or glucose) are, by the liv- 

 ing protoplasm, in some unknown way combined with nitrogen 

 and sulphur (probably also with salts, water, etc.), to form proteid 

 matter. The particles of this newly-formed compound are incor- 

 porated into the protoplasm (by " intus-susception, " p. -i) and, in 

 some way at present shrouded in mystery, are endowed with the 

 properties of life. We do not know how long they may remain 

 in the living state, but sooner or later they are oxidized, and, as a 

 result of the oxidation, that energy is set free which enables the 

 fern to do work and prolong its existence. The oxidized prod- 

 ucts are afterwards eliminated (excreted) from the cells. 



If a larger quantity of starch is formed in the chlorophyll 

 bodies than is immediately needed by the protoplasm for pur- 

 poses of repair or growth, it may be re-converted into starch 

 after journeying as glucose through the plant, and be laid down 

 as "reserve starch " in the parenchyma of the rhizome, or else- 

 where. Apparently, when this reserve supply is finally needed 

 at any point in the plant, it is again changed to glucose and trans- 

 ported thither. It is probable that new leaves and new tissues 

 generally, are always formed in part from this reserve starch, 

 and not solely from newly-formed starch. 



In dealing with the metabolism of the fern we may safely 

 assume, as we have done already for the earthworm, a constructive 

 phase (anabolimi) and a destructive phase (katabolism) ; but 

 these terms represent merely probable events, not known facts. 



The Outgo. The outgo, like the income, is of two kinds, 

 matter and energy, but it cannot be so readily tabulated. 



The plant suffers annually a great loss both of matter and of 

 potential energy in the production of spores and in the autumnal 

 dying-down of the fronds. But matter also leaves the plant 

 daily as carbon dioxide (in small quantities), water, and oxygen, 

 both by diffusion through the epidermis and by transpiration 

 through the stomata. Strictly speaking, the term outgo should 

 be restricted to the output of matter which has at some time 

 actually formed a part of the living protoplasm ; hence it does 

 not apply to the oxygen, which is simply given off in the maim- 



