THE BRYOLOGIST. 



1/ 



Vol. VI. March, 1903. No. 2. 



NOTES ON CERTAIN CLADONIAS. 



By Bruce Fink and Mabel A. Husband. 

 Plate VII. 



The western hemisphere surpasses the eastern in number of Cladonias 

 and in number of species peculiar to the hemisphere, hence the genus 

 should have a special interest for the American student of lichens. While 

 this is true, it remains a fact ,that our American descriptions of Cladonias 

 have been, without exception, wholly inadequate and many of our determina- 

 tions consequently incorrect. Cladonias are the most variable of all of our 

 lichens and therefore the most difficult to describe definitely. Fortunately, 

 the most variable characters are those which may be studied with the eye 

 or with a good hand lens, and yet nothing but the most careful observation 

 will enable one to determine a Cladonia with any degree of certainty even 

 with the best descriptions. Size, form, color, lobing and branching and the 

 presence or absence of cortex and soredia must be constantly kept in mind 

 in the consideration of the horizontal thallus and yet more in the study of 

 the podetia. 



As to microscopic examination, it may be said that the spores, usually 

 of considerable importance in determination, are here so constant in size and 

 form that they may usually be neglected in descriptions. The same may be 

 said of the algal cells. The so-called hypothallus is seldom seen and is of no 

 use in the determination of Cladonias. Also those doubtful structures, the 

 spermagones and the spermatia may be entirely neglected, while there is 

 serious doubt as to the diagnostic value of chemical tests in the determina- 

 tion of any lichens. The minute anatomy of the thallus may yet be found 

 to have some value in determination, but our investigations do not indicate 

 that it is of sufficient importance to warrant adding to the necessarily long 

 descriptions of such variable plants as the Cladonias. 



With this short preliminary statement let us pass to the consideration of 

 a few of the species; and we make no plea for beginning with the more 

 conspicuous and better known Cladonias, for there is urgent need for care- 

 ful study of every species. It is hoped that good descriptions of a few 

 Cladonias may enable those interested in these plants to observe some char- 

 acters usually quite overlooked. We have selected for description a num- 

 ber of Cladonias that are very commonly confused by American lichenists. 

 Cladonia rangiferina (L.) Web. in Wigger's Prin. Fl, Hols. 90. 1780. 



Primary thallus rarely developed, when present crustaceous, delicate 

 and composed of subglobose, depressed or irregular, clustered or scattered 

 verrucae, which are .20-. 40 mm. in diameter, ashy white and destitute of 

 cortical layer. Podetia, without cortex, arising from the surface of the ver- 

 rucae, or often as branches of old or dying podetia, or from free fragments 



The January BRYOLOGIST was issued December 27th, 1902. 



