72 DEGRADATIONS IN PARASITES [CHAP. 



eyebright, etc., would lead one to conclude 

 on a priori grounds that they could assimilate 

 carbonic acid just as ordinary flowering plants, 

 yet it has been discovered that the above- 

 mentioned genera, excepting the last, which in 

 other respects differs somewhat from its allies, 

 do not disengage oxygen in light, whatever be 

 its brightness or the method of investigation 

 employed. The interpretation of this remark- 

 able fact is that the assimilative power is so 

 enfeebled that the oxygen emitted is all re- 

 absorbed for respiration, there being no excess 

 to be given off as in the case of all non- 

 parasitic flowering plants. 



Great degeneracy of structure is seen in 

 both the vegetative and reproductive systems. 

 Besides the total absence of chlorophyll, the 

 leaves of such parasites which have none are 

 reduced to scales or are absent altogether. 

 The microscopic details follow suit in the 

 general absence of stomata, etc., while the fibro- 

 vascular cylinder of the stem exhibits various 

 anomalies, reminding one of the structures in 

 stems of climbing plants and of monocotyledons. 

 The great dislocation of the cords is a result of 

 parasitism, just as it is in climbing stems, and is 

 a result of an aquatic habit which has set up the 

 well-known arrangement in that class. 1 In the 

 case of the flowers of parasites a very common 



1 " Origin of Plant Structures," pp. 149, 198, 206, 214, 220. 



