Feb.,i893 parasites on ALG^. 121 



With the discovery by Alexander Braun (8) of a Chytridian 

 parasite on the fresh-water Alga Hydrodictyon, and the pubUcation, in 

 1855, in the paper quoted, of some twenty species of Chytriduon, many 

 of them inhabiting fresh-water Algae, a new field of research was 

 opened to cryptogamists. In the same year Bail (g) extended our 

 knowledge of the subject, and Cienkowski (lo), a little later, described 

 a Rhizidium parasitic on Conferva glomevata. Cohn (11), in a remark- 

 able paper on the physiology of the Florideae, pointed out, in 1867, that 

 Chytridia had been mistaken for fruits in certain marine Algae, 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 Algae, viz., 

 Chytridmm iumefaciens, in species of Cevamium ; C. sphacelavum, in 

 Cladostephus spongioses', and Sphacelai'ia cirrhosa and C.plnmula, in 

 CaUithamnion. Kny (13) next described another form — C. olla — in 

 the fresh-water CEdogonium rivnlave, 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., A ncylistes closteyii, which is of such singular character 

 that it is commonly reckoned by itself as the type of a group, 

 the Ancylisteae, 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 Chytridiaceae. These 

 Chytridiaceae 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 assemblage of forms with affinities in various 

 directions among Fungi, or even with Protococcaceae 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 

 Sapvolegnia, and are reproduced by the production of swarm-spores in 

 sporangial cells of definite shapes. These swarm-spores are provided, 

 as a 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 wall be found in 

 De Bary's Vevgleichendc Morphologie itnd Biologic der 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 Rahenhofsfs Kryptogamen-Flom, 

 pt. i., vol. iv., lieferungen 45 and 46 (1892), and by Schrceter in 

 Engler and Prantl's Natiivl. 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 



