18 



Bulletin 6 



covered the species in the Vosges district, to separate the 

 plant into a number of varieties. I have personally recog- 

 nized three of his variations in an individual plant, and if his 

 remaining segregates are equally valid it will furnish an inter- 

 esting exhibition of acumen gone wrong. Physcia stellaris is 

 another lichen observed in limited patches. The laciniae 

 were discrete after the manner of its variety leptalea, but 

 there were no marginal cilia found, and the form is insepara- 

 ble by any present criterion from the normal state. Physcia 

 stellaris is a pretty and common thing and has an almost uni- 

 versal distribution in temperate regions. Numerous varia- 

 tions of the species are to be found in Knox County, includ- 

 ing three forms unreported from America and one new and 

 undescribed thing. The variation aipolia of the species 

 occurred on our tree in the spermogoniferous state, so called, 

 that provides its most attractive exhibit, and growing in 

 greatest luxuriance, but not in its most attractive form, was 

 found Physcia tenella. This plant, scattered all over the 

 trunk wherever the bark provided attachment, was found in 

 the dispersed form and again in the more typical aggregated 

 state. Knox County has furnished the only known Ameri- 

 can example of the form exempta of this variation, the speci- 

 men serving to illustrate the close affinity of the variation to 

 the type. Another Physcia found in limited quantities was 

 P. tribacia. This interesting species is commonly found on 

 dead wood, and the fence beneath the tree supported it. On 

 neither tree nor fence was it found fertile, and fertile phases 

 are not by any means common. When found on rocks it pre- 

 sents its most attractive appearance, and to a beginner in 

 lichenology this condition is almost impossible of identifica- 

 tion. The late Prof. Clara Cummings, to whom I sent a 

 specimen of the rock form, stated: "I am not positive with 

 regard to your plant, but by the process of elimination it must 

 be Physcia tribacia." 



An interesting Pertusaria was P. lecanocarpa, an unde- 

 scribed species. The type of this species, likewise found on 

 elm, finds its nearest ally in P. multipuncta y but is sufficiently 

 diverse to be given specific rank. Another Pertusaria of 

 common and variable appearance is the Acharian P. amara. 

 This plant is indescribably bitter to the taste, and when in 



