50 A Monograph of the Myxogastres. 



I have given the author's own diagnosis of the species. 

 Scattered in cracks of the bark, from *5 1 mm. high, some- 

 times a little more, stem suberect, sometimes rather flexuous, 

 sporangium very small. 



CLATHROPTYCHIUM, Host. 



Aethalium naked ; sporangia sessile, prismatic or cylindrical, 

 densely crowded on a hypothallus, walls of sporangia persistent 

 at the apex, lateral walls reduced to 5 6 slender threads which 

 extend from the hypothallus and support the apical portion. 



Rost., Mon., p. 225 ; Cooke, Myx. Brit., p. 55 ; Schroeter, 

 p. 164; Sacc., SylL, p. 405; Zopf, p. 137. 



Rostafinski was the first to point out the true aethalioid 

 nature of Clathroptychium rugulosum, and in his diagrammatic 

 arrangement, Hon., fig. 30, represents the sporangia as circular 

 in outline, packed close together, and consequently leaving 

 triangular interspaces; each sporangium is represented as 

 having six triangular thickened portions of its wall projecting 

 into the interior of the sporangium. A careful examination of 

 several specimens in various stages of development show that 

 Rostafinski's interpretation is not correct. The sporangia, when 

 young, are cylindrical, with both ends slightly convex, and the 

 walls entire; towards maturity the lateral walls, due to mutual 

 pressure, become flattened, and the sporangia are then hexagonal 

 or rarely pentagonal in transverse section ; at the angles where 

 three contiguous cells meet the walls of the sporangia become 

 thickened, agglutinated together, and persist as the upright 

 threads that support the slightly convex, persistent, cap-like 

 portions of the sporangia. From the above description it will 

 be seen that the triangular upright threads correspond in 

 position to the triangular interspaces in Rostafinski's diagram, 

 and further, that the black triangular thickenings shown in 

 the diagram have no existence in nature. During the period 

 between the formation and maturing of the spores, the flat 

 lateral walls of the sporangia are dissolved, with the exception 

 of a narrow jagged wing projecting from each angle of the 

 upright permanent portions. In C. rugulosum these wings are 



