441 



Reinke contents himself with de Bary's definition of the Hchen 

 thallus ; de Bary designates it as the vegetative organ bearing the 

 apothecia, spermagonia, and in certain instances also pycnidia. 

 This rather negative definition is accepted by most modern lichen- 

 ologists who define the vegetative organ as the structure whose 

 prime function is to take up and assimilate food-substances. 

 Reinke also accepts, or at least expresses his disinclination to 

 change, de Bary's definition of the reproductive organs ; that is, 

 the reproductive organs are the apothecia and spermagonia. If 

 the experiments and observations of Stahl* and Sturgisf prove 

 correct it would be more correct to speak of the carpogone and 

 spermagone as the reproductive organs ; but since it is highly pro- 

 bable that the spermagonia are merely parasitic fungi, or since 

 their true nature is as yet problematical, we have no scientific au- 

 thority to designate them as reproductive organs. This difference 

 of opinion does not have any important bearing upon the question 

 under consideration. It is, however, evident that Reinke con- 

 siders the spermagonia as reproductive organs. 



Reinke recognizes two portions of the Cladonia-\}cvs^\x%: the 

 horizontal portion which is also called primary thallus or proto- 

 thallus, and the vertical portion, or the podetium of lichenolo- 

 gists. The term thallus is quite generally applied to the horizontal 

 or primary thallus, while the term podetium is retained to desig- 

 nate the vertical thallus. In all instances the podetmm takes its 

 origin from the gonidial (algal) zone of the horizontal thallus. 

 Whether the beginnings of the podetium are due to a sexual act 

 or not, is not definitely known. Krabbe and Reinke are inclined 

 to believe that it is nonsexual. Reinke, however, hints at a pos- 

 sible sexual act represented by a fusion of the nuclei of two neigh- 

 boring hyphal cells. 



The primary axis of the podetium is negatively geotropic, 

 thus differing essentially from the transversely geotropic dorsi- 

 ventral horizontal structure of the primary thallus. If the po- 

 detia branch, it is found that the negative geotropism decreases with 



* Stahl, E. Beitrage zur Entwickelungsgeschichteder Flechten, I. and II., Leip- 

 zig. 1877. 



f Sturgis, W. C. On the Carpclogic 'Structure and Development' of the CoUem- 

 aceae and Allied Groups. Proceedings of the American Acad. 25 : 1890. 



