ENDOSPORE^E. [pK'TYDTUM. 



SPECIES EXCLUDED FROM TIIE GENUS. 



C. mirabilis Mass. = Dictydium uinbilicatum Sclirad. 

 C. exilis Macbride = Dictydium umbilicatum Sclirad. 



Genus 24. DICTYDIUM Schrader, Nov. Gen. PL, p. 11 (1797). 

 Sporangia globose, stipitate ; sporangium-wall formed of parallel 

 ribs extending from the base to the apex, connected by slender 

 transverse threads, the intervening wall evanescent. 



1. D. umbilicatum Sclirad., I.e., p. 11 (1797). Plasmodium 

 purple. Total height 1 to 2 mm. Sporangia globose, cernnous, 

 0*5 to 0'7 mm. diam., dark red-brown ; sporangium-wall forming 

 a net with nearly square meshes, composed of numerous rigid 

 longitudinal ribs 5 ^ thick, connected by delicate transverse 

 threads ; basal cup scarcely developed. Stalk subulate, bent or 

 twisted at the slender apex, rich purple -brown, one to three 

 times the length of the sporangium. Spores pale red, minutely 

 warted, 4 to 7 /A diam., usually with two to four purple plasmodic 

 granules on the spore wall. Fr., Syst. Myc., iii., p. 165. Mucor 

 cancellatus Batsch, El. Fung., ii., 137 (1786). Stemonitis can- 

 cellata GmeL, Syst. Nat., p. 1468. Cribraria cernua Pers., Obs. 

 Myc., i., p. 91 (1796). Dictydium cernuum Nees, Syst. Pilze., 

 p. 120 (1816); Host., Mon., p. 229; Cooke, Myx. Brit., p. 57; 

 Blytt, Bidr. K. Norg., Sop. iii., p. 9 ; Macbride, in Bull. Nat. Hist. 

 Iowa, ii., p. 118. Heterodictyon mirabile Rost., Mon., p. 231. 

 Cribraria mirabilis Mass., Mon., p. 60. C. exilis Macbride, in 

 Bull. Nat. Hist. Iowa, ii., p. 378. 



Plate LVL, B. a. to d. sporangia of various forms after the dispersion of 

 the spores, x 36; a. typical form ; b. form with cup ; c. form with irregular 

 net, found with sporangia of usual type (England) ; d. erect sporangium 

 (United States) ; e. spore, x 600 ; /., g. type of Heterodietyon mvraUle 

 Host., x 70 (Freiburg, Germany) ; h. spores of same, x 600. 



The ribs of the sporangium-wall are inflexed at the summit in 

 maturity, and break the ball of enclosed spores by vertical pressure ; 

 they consist of two layers, the outer smooth and shining, the inner 

 beset with purple plasmodic granules 1 p. diam. ; they are usually free 

 at the base of the sporangium, but are sometimes connected by 

 an irregular basal disc. A form is occasionally found with a well- 

 developed cup having an evenly toothed margin from which the ribs 

 take rise ; associated with this character the stalk is more erect, and 

 of a browner colour than in the usual type ; the variety, however, 

 appears to be too inconstant to be marked as distinct. A careful 

 examination of the type specimen of Heterodictyfm mirabile Host., 

 in the Strassb. Herb., leads to the conclusion that it is a form of 

 Dictydium umbilicatum. It is no doubt a remarkable development ; 

 the basal cup is large and irregular, and the ribs in many parts are 

 expanded and form a loose, imperfect net with broad and angular 

 nodes ; in other parts the ribs are connected by the usual delicate 

 transverse threads, and though fewer in number and coarser than in 

 the type, are essentially of the same character ; they are thickly beset 

 on the inner side with purple plasmodic granules, the cup is also 

 studded with the same ; the spores are precisely similar to those of 



