DIDERMA 97 



4. DIDERMA SPUMARIOIDES Fries. 



1829. Diderma spiimarioides Fries, Syst. Myc., III., p. 104. 

 1833. Physaruni stromateum Link., Handb., III., p. 409. 

 1876. Chondrioderam stromateum (Lk.) Rost., App., p. 18. 



Sporangia sessile, crowded, spherical, or by mutual pressure 

 irregular, white ; the peridium plainly double, but the layers 

 adhering, the outer more strongly calcareous, but very frail, 

 almost farinaceous ; hypothallus more or less plainly in evi- 

 dence, white or pale alutaceous ; columella distinct, though 

 often small, globose, yellowish ; capillitium variable in quantity, 

 sometimes abundant, brown, somewhat branching and anas- 

 tomosing outwardly, the tips paler ; spores minutely roughened, 

 dark violaceous, about 10 /LI. 



This species has the outward seeming of a Didymium, but is 

 plainly different as that genus is here denned, in that the 

 calcareous crust, although inclined to be pulverulent, is made 

 up of minute granules, not crystals, of lime. The hypothallus 

 is sometimes hardly discoverable, anon well developed, out- 

 spread, rugulose, far beyond the limits of the fructification. In 

 his Monograph, p. 175, Rostafinski includes here PJiysarum 

 stromateum Link. In the Appendix he is inclined to raise 

 Link's form to the dignity of a distinct species, basing the 

 diagnosis upon the superposition of the sporangia in certain 

 cases, a feature entirely unknown to Link's description and of 

 extremely uncertain value, since by their crowding the spo- 

 rangia are liable always to be pushed above each other. We 

 therefore regard C. stromatenm (Link) Rost. as a synonym of 

 the present species, as the description, Link, Handb., III., 409, 

 indicates so far as it goes. 



5. DIDERMA GLOBOSUM Persoon. 



PLATE VII., Figs. 5, 5 a. 



1794. Diderma globosum Pers., Rom. N. Mag. Bot., I., p. 89. 

 1875. Chondrioderma globosum (Pers.) Rost., Afon., p. 180. 



Sporangia more or less closely gregarious, sessile, globose, 

 or by mutual pressure prismatic or polyhedral, white, the outer 



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