FEs., 1893. PARASITES ON ALG. 121 
With the discovery by Alexander Braun (8) of a Chytridian 
parasite on the fresh-water Alga Hydvodictyon, and the publication, in 
1855, in the paper quoted, of some twenty species of Chytrvidium, many 
of them inhabiting fresh-water Alge, a new field of research was 
opened to cryptogamists. In the same year Bail (g) extended our 
knowledge of the subject, and Cienkowski (10), a little later, described 
a Rhizidiwm parasitic on Conferva glomevata, Cohn (11), in a remark- 
able paper on the physiology of the Floridez, pointed out, in 1867, that 
Chytridia had been mistaken for fruits in certain marine Algze, and 
thus extended the domain of this group to the sea. He was soon 
followed by Magnus (12), who made known other forms, of which the 
following may be looked for by students of our native Algz, viz., 
Chytvidium tumefaciens, in species of Cevamium; C. sphacelarum, in 
Cladostephus spongiosus; and Sphacelaria civvhosa and C, plumule, in 
Callithamnion. Kny (13) next described another form—C. ol/a—in 
the fresh-water Cedogonium rivulare, and was succeeded by Nowakowski 
(14) and Professor Perceval Wright (15) with further records. In the 
meantime Pfitzer (16) described an interesting, novel parasite on 
Closterium, viz., Ancylistes closterti, which is of such singular character 
that it is commonly reckoned by itself as the type of a group, 
the Ancylistee, unless one puts with it Lagenidium, of which 
Zopf (17) described a form inhabiting Spirogyra, though there is now 
a disposition to include these forms under Chytridiacee. These 
Chytridiacee are a group of Fungi of aberrant type, and it is 
still debatable whether they form one natural family, or are better 
considered a convenient assembiage of forms with affinities in various 
directions among Fungi, or even with Protococcacee among Algae. 
Both views claim a good deal of support, but much remains to be 
done in working out the life-histories. They are parasites in the 
tissues of marsh and aquatic plants, including aquatic Fungi such as 
Saprolegnia, and are reproduced by the production of swarm-spores in 
sporangial cells of definite shapes. These swarm-spores are provided, 
asa rule, with only one cilium, and they develop without well-marked 
intermediate stages into fresh sporanges. Some forms have resting 
spores which develop in similar fashion. They are all exceedingly 
minute, and easily find lodgment in the cells of their hosts, on which 
they produce both destructive and deforming effects. An excellent 
general account of their life-histories and operations will be found in. 
De Bary’s Vergleichende Morphologie und Biologie dey Pilze, of which the 
Clarendon Press has published an English translation by Garnsey and 
Balfour, while the latest systematic accounts of them (both well 
illustrated) are by Alfred Fischer in Rabenhorst’s Kryptogamen-Flora, 
pt. i., vol. iv., lieferungen 45 and 46 (1892), and by Schrceter in 
Engler and Prantl’s Naturl. Pflanzenfam., lieferung 76, p. 64. Not 
the least interesting circumstance about them is their occurrence in 
the sea, since it is well known that even such aquatic Fungi as the 
Saprolegnia of the salmon-disease find immersion in salt-water rapidly 
