i 9 i2] CURRENT LITERATURE 541 



grows on rocks that contain no organic matter. Breathing pores have been 

 postulated for the lichens in a general way, but we really know little about 

 provision for exchange of gases in these plants. The student will find a general 

 summary by Funfstuck in Engler and Pjrantl's NatUrlkhen Pflanzen- 

 familien. In 1906 Zoep 3 described a new Ramalina (R. kullensis) which has 

 the so-called breathing pores well developed, and Rosendahl 4 in 1907 found 

 them in Parmelia aspidota. Nothing more seems to have been added to 

 Funfstuck's statement, and it appears probable that passages from the 

 exterior to the interior of lichen thalli are rare instead of common. 



Tobler 5 thinks that such passages may be expected in thalli with thick 

 cortices, but scarcely in those with thin cortices, where sufficient aeration may 

 occur without them. He believes that the lack of sufficient air and light 

 within the lichen thallus makes the conditions unfavorable for the alga and that 

 this accounts for the layering of the algae near the surface of the thallus. 

 Tobler cultivated Xanthoria parietina and a number of other lichens without 

 algae in a gelatin-beerwort medium and got a rich production of calcium 

 oxalate. He then cultivated the thalli with the algae and was not able to find 

 the oxalate. He supposes, therefore, that the algae used the surplus extracted 

 from the medium by the lichen, and that the same occurs in nature, the lichen 

 taking the oxalate from the organic substratum. We may add that according 

 to Elenkin's 6 theory of endosaprophytism, the lichen may extract organic 

 compounds from the dead algae for the living. 



Treboux 7 is cited by Tobler to the effect that species of Chlorella, 

 Pleurococcus, Cystococcus, and some other algae investigated, are able to 

 obtain carbon in a very different manner from that known in higher green 

 plants. 'It was found that these algae are able to thrive on artificial media 

 containing organic acids, and the conclusion was reached that they behave 

 much like fungi with respect to carbon assimilation. 



Tobler failed to notice the excellent work of Artari, 8 performed on algae 

 which grow in lichen thalli, to ascertain the physiological relationship of the 



3 Zofp, W., Biologische und morphologische Beobachtungen iiber Flechten. II. 

 Ber. Deutsch. Bot. Gesells. 24:574-580. pL 23. 1906. 



4 Rosendahl, F., Vergleichende anatomische Untersuchungen iiber die braunen 

 Parmelien. Nov. Act. Kais. Leop. Karol. Akad. 87:404-459- pk- 25-28. 1907. 



5 Tobler, F., Zur Ernahrungsphysiologie der Flechten. Ber. Deutsch. Bot. 

 Gesells. 29:3-12. 1911. 



6 Elenkw, A., Zur Frage der Theorie des Endosaprophytmus bei Flechten. 

 Bull. Soc Imp. Nat. Moscou II. 18:164-186. 1904. 



7 Treboux, O., Organische Sauren als Kohlenstoflquelle bei Algen. Ber. 

 Deutsch. Bot. Gesells. 23:432. 1905. 



8 Artari, A., tJber die Entwickelung der griinen Algen unter Ausschluss der 

 Bedingungen der Kohlensaure Assimilation. Bull. Soc. Imp. Nat. Moscou II. 23:39- 

 47. figs. 2. 1899. 



