1885.] 



MICROSCOPICAL JOURNAL. 



171 



zoids not obsei-ved, but in a few cases 

 copulation of two similar swarm 

 spores has been seen. The product 

 of such copulation is a zygospore 

 (isospore) which passes through a 

 resting stage, then grows and produ- 

 ces unsexual zoospores, which pro- 

 duce new plants. 



Usually propagation takes place by 

 the formation of One or numerous 

 asexual zoospores within each cell. 

 These are colorless at the front end, 

 with a red pigment spot, and 2 cilia 

 (microzoospores) or 4 cilia (macro- 

 zoospores) . Both kinds are common 

 Ln some genera, but only the micro- 

 zoospores can copulate. 



Resting cells of various kinds are 

 found in most genera. 



FAMILIES. 

 Filaments branched or unbranched, 

 with or without gelatinous envelopes, 

 cells sometimes ending in long bristles. 



CONFERVACE^, VI. 



Filaments branched, upper part of 

 cells swollen, all endochrome passing 

 from the lower part into the swollen 

 portion. Pithophorace-«, VII. 



PamilyW. CoNFERVACEyE. 



Branched or unbranched filaments, 

 cell-walls either delicate or thick, 

 -sometimes distinctly lamellose, with 

 or without gelatinous envelopes or 

 sheaths ; terminal cells sometimes 

 ending in long bristles or hyaline 

 points. 



Propagation by macro- and micro- 

 zoospores, in some genera by resting- 

 spores. 



A. Filaments unbranched, or at 

 most with short, latei^al rhizoids ; ter- 

 minal cell without hair-like termina- 

 tion. 



Zoospores of two kinds, macro- 

 zoospores vs'ith 4 cilia, microzoo- 

 spores with 2 cilia, 8 many in a 

 single cell, which may copulate, or 

 vegetate w^ithout copulating. Copu- 

 lation produces a zygospore, which 

 grows slowly to an unicellular plant, 

 that produces a number of macrozoo- 

 spores. Other resting-spores not ob- 

 served. (Ulotrichin^). 



B. Filaments branched ; lower cells 

 converted into colorless rhizoids, ter- 

 minal cells often provided with long 

 hairs or bristles. (Cladophorin^e) . 



a. Cell-walls delicate, 2-16 zoo- 

 spores formed in one mother- 

 cell, with 4 cilia, set free by rup- 

 ture or swelling up of the mother- 

 cell. (Ch.etophore^). 



b. Cell-walls thick ; zoosporesvery 

 numerous (at least 32) in one 

 cell, set free through an opening 

 in the cell-wall, with 2 or 4 cilia. 



(Cladophore^e) . 



c. Spreading, flat, in a single layer 

 of cells, either leaf-like, smooth, or 

 crisped, or in the form of a hollow 

 tube. (Ulvin^) . 



A. Ulotrichin^. Group i. 

 Synopis of Genera. 

 Filaments tortuous, with short lateral 

 proliferations. Rhizoclonium., 55. 

 Cells rarely exceeding diameter in 

 length ; walls delicate. 



Ulothrix., 56. 



Cells longer, usually turgid, contents 



granular. Cotiferva., 57. 



Filaments like Ulothi'ix., parallel, in 



gelatinous envelope. 



Schizogonium., 58. 

 Filaments large, not branched ; w^alls 

 distinctly lamellose and thick. 



Chcetoinorpha^ 59. 



55 . Genus Rhizoclottium Kiitzing. 



Filaments like Conferva., but dis- 

 tinctly tortuous (bending back and 

 forth), with short, lateral, pointed 

 proliferations or rhizoids. 



56. Genua IHot/irix Kiitzing (ex- 

 tended) . 



Simple filaments, basal cell ex- 

 tended to a rhizoid. Macro- and 

 microzoospores, the latter copulating 

 (as observed in U. zonata) ; both set 

 free while the cell-walls sw^ell atid 

 break up. 



[The genus as thus constituted in- 

 cludes Hormiscia^ Areschoug, a 

 genus usually recognized, character- 

 ized mainly by thick and robust cell- 

 walls, often distinctly lamellose. 



In the sterile condition it is difficult 

 to distinguish between Conferva and 



