1916 Kibbej on Chytridium 223 



appears to be the additional over-crowding of the fruiting layer, due to 

 the great number of fungus sporangia. Both host and parasite have spo- 

 rangia which are small at the base and broad at their outer ends (Fig. 5). 

 Comparatively few parasitic fungi having marine algae as hosts have 

 been described. Lemmerman (7) names only one marine form, Dothidella 

 laminariae, a Pyrenomycete, although he names 192 species parasitic on 

 fresh water algae. Estee (2) describes another Pyrenomycete which she 

 calls Guignardia irritans, parasitic on Cystoseira osmundacea and Halidrys 

 dioica. Patouillard (8) describes Zignoella calospora parasitic on Cas- 

 tagnea chordariaeformis. Patouillard and Hariot (9) found Zignoella 

 enormis on Stypocaulon scoparium. Jones (5) found Sphaerella chondri, 

 a fungus similar to Guignardia irritans, on Chondrus crispus. Souther- 

 land (11, 12, 13) has found several Pyrenomycetes parasitic on marine 

 algae. Reed (10) describes two ascomycetes, Guignardia ulvae on Ulva, 

 and Guignardia alaskana on Prasiola. Griggs' (4) figures of Phodochy- 

 trium suggest the fungus on Alaria somewhat, but in Rhodochytrium the 

 spores are formed endophytically. 



Of the Phycomycetes several species are known on marine algae. 

 Cohn (1) describes Chytridum polysiphoniae on Polysiphonia violacea, 

 Olpidium (Chytridium) plumulae on Antithamnion plumula, and Olpidium 

 (Chytridium) entosphaericum on Bagnia fusco-purpurea and Hormiscia 

 penicilliformis. Fisher (3) also cites in literature not available Rhizophi- 

 dium dicksonii on Ectocarpus, Olpidium sphacellarum on Sphacelaria and 

 Cladostephus, Olpidium tumaefaciens on Ceramium, Olpidium hryopsidis on 

 Bryopsis plumosa, and Olpidium aggregatum on Cladophora. 



Thus there are reported as growing on marine algae so far as the 

 writer could find several Phycomycetes, among which is one Chytridium; 

 a considerable number of Ascomycetes, most of which are Pyrenomycetes ; 

 and no Basidiomycetes. 



A search of the available literature failed to disclose any species to 

 which this plant could be referred. However, its life history, so far as 

 it could be studied with the available material, seems to refer it to the genus 

 Chytridium. Since it grows parasitic on Alaria, it is named as follows: 



Chytridium alarium sp. nov. Vegetative portion of the fungus 

 intracellular, spherical at first, becoming oblong, without hyphae, some- 

 times with short rhizoids which press in between the cells and into the 

 walls of the host but do not pierce them, otherwise unbranched. Spo- 

 rangium oblong, about 75/x long and 20-2 5/x in diameter, smooth, brown. 

 Spores (probably 300 spores but cilia not seen) 3-4^ in diameter, spherical 

 or nearly so. Sexual reproduction unknown. Parasitic on Alaria fistulosa. 

 The writer gratefully acknowledges the advice of Dr. J. W. Hotson 

 and Dr. T. C. Frye. 



