FL.VCTION.] oF BROWN PARASITES. 321 



tion of plants which are not green; as to the solar light 

 it has but a feeble influence on this phenomenon, and it 

 is probable that it only acts by the elevation of temperature 

 which necessarily accompanies exposure to the direct rays of 

 the sun. If some of these plants, certain Orobanchese, appear 

 to seek the light at their flowering period, it is doubtless 

 because they have need of solar heat to favour the active 

 respiration established in their floral spike. 



At a mean temperature of 18 cent. O. Teucrii in full flower, 

 placed in the air, destroys in thirty- six hours more than four 

 times its volume of oxygen, viz. 4-2 cmc. per gramme ; 

 which is equivalent to a loss of 2*26 milligrammes of carbon 

 per gramme. After flowering, the phenomenon becomes much 

 less intense ; the stems of the same species, of which all the 

 flowers were faded, only gave 2- 6 8 cmc. of carbonic acid per 

 gramme in thirty-five hours. 



The flowering part of the stem of O. brachysepala destroys 

 in the same time, cateris paribus, two-thirds as much oxygen 

 as the flowerless part of the same stem. The difference would 

 be still more striking, if the oxygen absorbed by the flowers 

 alone were compared with that consumed by the rest of the 

 plant. But the manner of respiration is not the less the same 

 at all the stages of growth and for all the organs of the 

 plant. 



Thus the respiration of Orobanchese, and of plants 

 which are not green in general, is precisely the inverse 

 of that of green plants, at least during the day* To make 

 this difference more sensible, I subjoin the following ex- 

 periment : 



I took a piece of Orobanche Teucrii, the flowers of which 

 were not yet expanded, and also a portion of the leafy stem 

 of Teucrium Chamaedrys, each specimen weighing 7*5 grains ; 

 they were placed in two receivers, the capacity of each being 

 220 cmc. ; these were filled with a mixture of six volumes of 

 air and one volume of carbonic acid, and exposed to the light 

 from nine in the morning till three in the afternoon of the 

 next day, in a place where they received the afternoon sun. 

 At the end of this time the gas, in the jar containing the 



VOL. II. Y 



