Scrophulariaceae. 499 



С. Parasitism. 



As is well-known the Euphrasia spp., Bartschia alpina and 



the Pedicularis spp. are green semiparasites. 



As regards their capability of assimilating the carbon 

 dioxide of the air, Heinricher (1910, VI, p. 574) states that 

 in the Euphrasia spp. this is almost normal, and the same 

 author also attributes active assimilation to Bartschia. Vol- 

 kart (1899, p. 30) sums up his results as regards the Pedi- 

 cularis spp. {P. recutita, foliosa and verticillata) investigated 

 by him as follows: "Die Versuche zeigen, dass die Stärke- 

 speicherung der Blätter der untersuchten Pedicularisarten 

 normal und ohne grosse Abweichung von denjenigen anderer 

 Pflanzen vor sich geht. Eine weitgehende Herabsetzung der 

 Assimilationstätigkeit durch den Parasitismus, wie sie Bon- 

 nier aus seinen Versuchen ableitet, findet nicht statt." 



In this connection I wish to draw attention to the fact 

 that the mesophyll, in all the Rhinantheæ spp. investigated 

 by me, was found to be normal in structure, and its cells 

 contained a normal supply of chlorophyll grains. 



Bartschia alpina according to Heinricher's investiga- 

 tions, is an obligate parasite. According to Volkart, the 

 Pedicularis spp. may show gradations in their dependency 

 on other plants; from P. palustris^ which he describes as 

 "Stärkster Parasit mit stark entwickelter Neigung zur sapro- 

 phytischer Ausnützung der Nährpflanze" (by the destruction 

 of the roots attached), to P. comosa, which is said to be a 

 "Relativ seibeständig entwichlungsfähige Art"; as regards 

 P. Oederi he writes "Saprophytische und hydroparasitische 

 Ausnutzung der Nährwurzel gleichgestellt." 



From the Arctic regions we lack accounts of thorough 

 investigations regarding this matter; but as regards P. lanata 

 there is a note to hand which might suggest that under 



