148 
ENDOSPOREyE. 
[dictydium. 
SPECIES EXCLUDED FROM THE GENUS. 
C. mirahilis Mass. = Dicti/clium umbilicatum Schrad. 
C. eccilis Macbride = Dictydium umbilicatum Schrad. 
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. umhilicatum Schrad., I.e., p. 11 (1797). Plasmodium 
purple. Total height 1 to 2 mm. Sporangia globose, cernuous, 
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 /a thick, connected by dehcate 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 /x 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); Post., 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 Post., 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 cl. sporangia of various forms after the dispersion of 
the spores, x 36 ; «. typical form ; h. form with cup ; c. form with irregular 
net, found with sporangia of usual type (England) ; d. erect sporangium 
(United states) ; c. spore, x GOO ; /., g. type of Heterodictyon mirahile 
Eost., 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 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 Heterodictyon mirabile Host., 
in the Strassb. Herb., leads to the conclusion that it is a form of 
Dictydium unihiUcatum. 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 
