Johnson — Chri/sophlyctis endobiotica and other Chytridiacece. 143 



the representative of a new genus which he calls Eurychasma {Eurus broad, 

 kasma a slit). It lives entirely in the interior of the host-cell attacked, does 

 not produce rliizoids (i.e., it has no intramatricular mycelium), and its whole 

 vegetative body becomes converted into a zoosporangium. It is thus 

 holocarpic. Eesting spores are unknown. It differs from the other 

 Monolpidiaceae in which Wille placed it by the mode of deliiscence of its 

 sporangium. This splits open and forces apart the cell-wall of the host-cell, 

 projects through the opening made, sends out one or two slight prominences, 

 tlie ends of which open to allow its zoospores to escape. Euri/chasma 

 Dicksonii (Wright) Magnus is the only species. It is very widely distributed, 

 and has been recorded from the coasts of Ireland, Scotland, Norway, and 

 from the Adriatic. It grows on many species of Ectocarpus, on Pylaiella 

 littovalis, and on Striana attenuata. Hauck found it in localities in the 

 Adriatic where the sea-water was not pure. Fischer states that the 

 Chytridiaus prefer pure water, and that when, e.g., cultures of decaying 

 algae which Chytridiaus are destroying begin to smell badly, the Chytridians 

 themselves are soon destroyed. Macerations are, however, recommended by 

 several observers for the germination of the resting spores. 



Ol^ndium sphacellanim Kny is another marine form not uncommon on 

 species of Sphacelaria from various parts of the Irish coast, and hitherto 

 unrecorded. It occurs in the apical cells of the main and side shoots of 

 Sphacelaria and Cladostephus. Its sporangia, one to nine in each cell, are 

 rounded or flattened by pressure, have a smooth wall and a quite short 

 projecting emptying-neck. Resting spores are unknown. The host-cells 

 attacked cease dividing, become club- or pear-shaped, and their contents, 

 when not absorbed, turn brown or blackish. 



No group of plants has more frequently led to error than the Chytridians 

 which simulate the reproductive organs of tlie marine algse. I have to 

 confess myself at fault (19) in describing a Chytridian, possibly this 

 Olpidiura, as the sporangia of Desmarestia Ugultda, which thus still awaits 

 the discovery of its reproductive organs. 



The following list of Chytridiacese on marine algae, given by A Fischer 

 (op. cit., p. 26), may be of use to Irish students : — 

 Olpidium bryopsidis on Bryopsis. 



„ agyregatum in Cladophora. 



,, sphacellarum Kny. 



„ entosphmricum in Bangia and Hormidium. 



,, tumwfaciens in Ceramium. 



„ plumulce in Antithamnion plumula. 



