PLANT RESPIRATION 101 



them out of its body; but the plant, bcinir in every respect a 

 more economical machine, changes their chemical nature and 

 builds them up again into some sort of ])rotein material. Tliis 

 means that the energy liberated by the breaking down of 

 proteins is used in building them up again, so that i'ar less 

 energy is available in the plant for movement and for the 

 production of heat. Plants move hardly at all, and the 

 temperature even of a passion-flower or a tiger-lily varies 

 not at all from that of the surrounding medium. 



But an interesting fact has recently been noted. Just as 

 our temperature rises when we are attacked by the bacteria 

 which produce, say, diphtheria or enteric fever, so the tem- 

 perature of a sick grape-fruit or an invalid orange rises by 

 1 to 1|^ per cent., or even 2 per cent, when the fruit is infected 

 by a fungus, so long as it be alive. If the infection takes place 

 in the dead fruit no increase of temperature occurs. These 

 facts, which require further investigation, will doubtless greatly 

 assist those in charge of the transport of fresh fruit, which has 

 already attained enormous proportions, all over the world. 



Plants have no respiratory organs. No special part of their 

 body is set aside for the taking in of oxygen and the giving 

 out of carbon dioxide. As we have seen, the plants, especially 

 their leaves, are permeated by channels" and spaces. The cells 

 of the flowering plant do not fit close together; intercellular 

 spaces exist where three or four cells meet. Into these channels 

 and spaces the air penetrates and oxygen is taken up through 

 the walls of the cells and through the same w^alls carbon 

 dioxide passes from the cell into these intercellular spaces and 

 then leaves the body of the plant. Plants, as it were, breathe 

 all over and throughout the body. The period a plant can 

 survive in the absence of oxygen varies. The higher plants, 

 at any rate, do not live long in the absence of this gas. They 

 succumb to the accumulation of such poisonous products 

 as carbon dioxide. Even such inert things as seeds, if kept 

 without oxygen, soon die. 



Respiratory Organs in Animals 



The lower multicellular animals, such as sponges and jelly- 

 fish, take in oxygen all over and throughout the body. The 



