Howe: Preliminary notes on the genus Usnea 313 



USNEA BARBATA FLORIDA (L.) Fn 



This IS a distinct and easily recognized subspecies, the tufted 

 thallus rarely if ever attaining a development of over 12 cm. The 

 apothecia reach a diameter of 25 mm.* Infertile conditions are 



^ 



not uncommon, and are abundant if we do not recognize barbata^ 

 and if we hold that Jiirta and rubiginea are merely contingent 

 phases. In the so-called variety hirta^ with the failure to develop 

 apothecia, due presumably to lack of sufficient moisture, the plant 

 often becomes hirsute (and now blackening with age), and is more 

 or less sprinkled with soredia, the distal portions of the filaments 

 often becoming confluently crusted, or sorediate. But this sore- 

 diate condition is not absolutely confined to fiorida^ but is present 

 occasionally in all forms,t and the difficulty of recognizing it by a 

 name is at once apparent. No doubt \{ some of our foliose hchens 

 were not so constant morphologically, the sorediate subspecies 

 now recognized would appear as absurd as in the present instance. 

 The stress of the original separation of this form, it has been said, 

 was laid, as the name would imply, on the hirsute \ character, the 

 sorediate condition being of secondary importance. 



Rubiginea^ plainly, it appears to me, \s a case of dichromatism, 

 and in other branches of science, ornithology, for example, dichroic 

 conditions are not invariably named, /. ^., Megascops\Ottis\asio (L.). 

 Later it will be seen that filamentous forms are occasionally also 

 dichroic, though the fertile ^orida is rarely affected. § By way of 

 explanation, the dichromatism seems perhaps to be due to some 

 sort of dye that attacks mainly the infertile forms — possibly fol- 

 lowing up the cortex, and sometimes staining the cottony portions 

 of the medulla outside the indurated cord. This explanation is 

 suggested by the fact that the proximal portions are generally first 

 colored, though this is not always true. The color on the other 

 hand may be due to a morphological change as a result of age, 



* Mexican specimen. 



f Schaerer, 1839, says ol ceraiina '* glabra vel verrucoso-pulverulenta." 



X See first supposed reference, before Linnaeus' description : Tragus, H., ** Muscus 

 arborum villosus incanus," etc.; Schaerer, 1839, defines "verrucoso-pulverulenta, 

 fibrillosa et efibrillosa"; Linnaeus' original description reads: " Lichen filamentosus 

 ramosisRimus erectus, tuberculis farinaceis sparsis." Ilirius would then seem probably 

 used in the sense of rough. 



^Michaux, A., Flora Boreali-Americana 2: 332. 1819: "minus hirta, nibi- 

 gineo-rubens ; scutellis concoloribus." Sorediate specimens are frequently dichroic. 



