236 AQUATIC PHYCOMYCETES 



Sporangium flask-shaped, except for apex of neck immersed in the 



host sheath, usually stalked; on Apiocystis R. anomalum, p. 287 



Sporangium predominantly obovoid, obovate, or obpyriform 1 



Section III, p. 288 

 Zoospores liberated upon deliquescence of the upper half of the 



sporangium wall; on diatoms R. clinopus, p. 288 



Zoospores liberated upon formation of one or more apical, sub- 

 apical, or lateral discharge pores 

 Sporangium sessile on gelatinous colonial sheath of the host, 

 borne on the tip of a long threadlike stalk which penetrates 

 the host cell, with two subapical, opposite discharge papillae; 



on Gemellicystis R. fitlgens, p. 289 



Sporangium sessile on the host cell proper 



Sporangium with a single lateral pore; on Oedogonium 



R. parasiticum, p. 290 

 Sporangium with an apical pore 



Discharge pore very broad, its edge reflexed; resting spore 

 spiny, without an adherent male cell ; on Glenodinium 



R. echinatum, p. 290 

 Discharge pore smaller, its edge not reflexed; resting spore 

 smooth-walled, resting on a small male cell; on Stigeo- 



clonium R. ovation, p. 291 



Sporangium predominantly citriform or saddle-shaped, ovoid or 

 oblong, or spherical at first but becoming broadly ellipsoidal or 

 fusiform; the long axis of the sporangium parallel with the sur- 

 face of the substratum Section IV, p. 292 



Resting spore spherical or subspherical, without an adherent male 



cell; on Chlamydomonas and Goniitm R. transversum, p. 292 



Resting spore spherical, oval, or polygonal, with a male cell adherent 

 or connected to it by a conjugation tube of variable length 

 Resting spore spherical, with radiating columnar bands of refrac- 

 tive material in its wall; male cell connected by a conjugation 

 tube of variable length ; on Spirotaenia .... R. columharis, p. 293 

 Resting spore oval to subspherical, wall homogeneous ; male cell 

 directly adnate or connected by a short tube to resting spore 

 Sporangium saddle-shaped, on Stylosp/uwriclium or epiphytic on 



Coelosp/iacrimn R. ephippium, p. 294 



Sporangium oblong to oval, on Dinobryon R. oblongum, p. 295 



Resting spore polygonal, with one or two small adherent male 



cells ; on Tribonema R. goniosporum, p. 295 



Sporangium predominantly cylindrical, fusiform, broadly or narrowly 

 ellipsoidal or angular: the long axis frequently at right angles or 

 slightly inclined to that of the substratum Section V, p. 296 



1 See note 2, p. 231. 



