loosely covering, partly rather closely clinging to the latter. It is attached with numerous rhizoids. 

 New crusts are now and then formed upon the primary one, or covering foreign bodies which 



have attached themselves to the plant and 

 tli en partly also extended over the primary 

 crust, sometimes at length rather irregularly 

 developed and a little curled (Fig. 28). 

 The crust here and there gfrows free, but 

 it does not form divided branches. It is 

 very brittle in a dried stage. A vertical 

 section of the plant exhibits cells which are 

 rectangular, 50 — 100 fx. long and 15 — 35 y . 

 broad (Fig. 29). The conceptacles of spo- 

 rangia are conical, 1 — 1,2 mm. in diameter, 

 when seen from above. A few sporangia 

 examined were young, indistinctly four- 

 parted and 160 — 200 y.. in length by 80 — 

 100 a. in breadth. The plant is furnished 

 with these organs in the month of December. 

 Although there are some species of 

 this genus which are unsumciently known 

 and hardly recognizable from the descrip- 

 tions, I venture to place the plant in 

 question as an independent species, having been unable to identify it with any formerly described 



one. In habit it closely approaches to 

 young specimens of M. macrocarpa, 

 but, as far as hitherto seen, it does 

 not form branches, though it shows a 

 tendency to divide itself. M. macrocarpa, 

 on the other hand, forms branches in a 

 stage as young as the specimens known 

 (if M. a f/i 'nis. In a section the cells of the latter species are larger than those of the former 

 one. However, the most certain distinguishing feature lies in the conceptacles of sporangia. I 

 have measured numerous conceptacles in M. macrocarpa from different places, but I have not 

 met with larger ones than about 800 u.. in diameter. In the species in question, on the other 

 hand, they are of the size stated above and about as large as in M. Lamourouxii. Therefore, 

 the plant seems to be well defïned from M. macrocarpa and cannot, at present at least, be 

 considered as a form of this species. In several species, particularly of other genera, the 

 conceptacles are certainly much varying in size which, however, does not seem to be the case 

 in the here mentioned ones. M. Lamourouxii in a young stage apparently never extends 

 ily as M. af/iuis, and the thallus is thinner. The conceptacles of sporangia in 

 M. Lamourouxii vary between 1 , 1 and 1 , 3, seldom up to 1,4 mm. in diameter, and they 



Fig. 28. Mastüfhora affinis Fosl. 



Cruslily expanding over the branches of Polyopes constrictus\ 



nat. size. 



Fig. 29. Mastophora affinis Fosl. 

 Vertical section of the crust; X 72. 



