COLLEMA. 143 



layer, ivhich becomes at length distinct. Spores from simple and 

 ovoid-ellipsoid becoming bilocular, and elongated and bi-quadri- 

 plurilocular, icith entire sporoblasts ; only exceptionally sub-muri- 

 form. 



2. C. myriococcum, Ach., Arn.; thallus of middling size, 

 sub-orbicular, cartilagineous ; black ; attached closely to the sub- 

 strate in the manner and with the look of Nostoc Commune; 

 the irregular, flexuous, variously complicated lobes repand, and 

 more or less warted ; apothecia minute, crowded, immersed, or 

 emergent, lecanorine, the pale-brown disk bordered at length by 

 a persistent margin. Spores rounded-ovoid and ellipsoid, eirn- 



ple, decolorate, ^ mic. Ach. L. U. p. 638. Arn. Fragm. in 



Flora, 1867. Tuckerm. Gen. p. 89. 



Calcareous rocks, growing over mosses, Rockland County, 

 New York (Austin), Tuckerman I c. 1872. What is with little 

 doubt the same plant but infertile, has occurred, in similar sta- 

 tions, at Trenton Falls, N. Y., Tuckerman ; in New Jersey, Aus- 

 tin ; and in Alabama, Peters. 



The C. chalazanum of Leigh ton Lich.-Fl. Brit. p. 17, if we 

 may judge by an Irish lichen of Herb. Taylor, is scarcely separable 

 from the present ; and Nylander (Lich. Scand. p. 29) has ques- 

 tioned the specific distinctness of the two; but, according to 

 Arnold, the former is kept apart by longer and larger spores 

 (Hepp. n. 662). The shape of the spores is however quite uncer- 

 tain ; and the supposed difference in the thekes is no more, in 

 our plant at least, to be depended on ; these organs occurring 

 now narrowed, with the spores in a single series, and now ventri- 



cose. The apparent distance between the present species and 



the one next following might seem perhaps to be reduced by C. 

 omphalarioides, Auz. (Lich. Etrur. n. 46), which Arnold has re- 

 ferred to the group represented by C. myriococcum (Lempho- 

 lemma, Koerb.), but the relation of the Italian lichen to C. pyc- 

 nocarpum appears to be far more intimate than to any form of 

 the other group. 



3. C.pycnocarpum,Ny}.; thallus middling-sized, sub-orbicu- 

 lar, membranaceous-cartilagineous ; from pale- becoming black- 

 ish-green ; lobes radiately expanded, soon irregularly narrowed, 

 fenestrate, ribbed, with ascendant marginal lobules which are 

 densely rugose-lobulate, and covered at length with the crowded 

 fruit concealing the thallus ; apothecia small, disk red, soon con- 



