PALMELLACE^. 



[ 574 ] 



PALMELLACEzE. 



of the minute granules or cells, wliicli are 

 the discharged contents of the larger cells. 

 The red cells of the red-snow plant turn 

 green when exposed to light, if kept moist. 

 An exactly similar plant has heen given us 

 by Mr. Oliver, from Crag Lough, North- 

 umberland, in a fresh condition ; and v^e 

 have never been able to detect any moving 

 forms in it. Further particulars are given 

 under Rkd Snow and Water. Several other 

 species of Pahnella are described ; but most 

 of them are too imperfectly known to allow 

 of definite characters being given ; P. rosea 

 is perhaps a good species. The forms with 

 a definite frond formerly placed here (P. 

 pi'otuberans, hotryoides, &c.) will be found 

 under Coccocitloris. 



BiBL. Eng. Bot. pi. 1800 ; Greville, Alg. 

 pi. 205; Meneghini, Tr. Turin Ac. 2. v. 

 pi. 6 ; Hassall, Alg. pi. 80 : Niigeli, Alg. G6, 

 pi. 4D; Kiitz. 'Sp. Alg. 211; Rabenht. 

 Alg. iii. 32. See also Red Snow, and Pro- 



TOCOCCUS. 



PALMELLA'OE^.— A family of Con- 

 fervoid Algae, consisting of gelatinous or 

 pulverulent masses, growing on damp sur- 

 faces, in fresh water or in the sea ; composed 

 of globular or elliptical cells, either more or 

 less adherent together into a definite or 

 indefinite pseudo-membrane or frond, or 

 loosely aggregated within a definitely or 

 indefinitely formed gelatinous matrix, or 

 loosely coherent in the form of a pulverulent 

 crust. Some authors have imagined that 

 the cells of Coccochloris or Pahnella are at- 

 tached to filaments included in the gelatinous 

 frond: this seems an error (seePALMELLA). 

 Yellowish or bluish-green, or red, often 

 varying from green to red, and vice versa, 

 during the course of development. In- 

 creased by cell-division into two or four, 

 and by ciliated zoospores. Many exhibit 

 three forms: — 1. active; 2. quietly vege- 

 tating by subdivision ; 3. resting form, 

 with a tough membrane. We include here, 

 for the sake of convenience, not only the 

 true Palmellacese, where there is a frond 

 composed of a number of cells held together 

 by mucus, but also all those Unicellular 

 Algfe which, from their mode of increase, 

 are found living socially or in masses which 

 appear like Palmelloid plants. 



Synopsis of Genera, 



* Cells immersed in a colourless gelatinous 

 frond. t Frond amorphous. 



Pahnella. Frond a slimy stratum, crowded 



with rather large globular green and red 

 cells, multiplying by division (PI. 7. fig. 3). 

 Microhaloa. Frond mucoid, floating in 

 water, densely cro\\ded with minute cells, 

 multiplying by di^sision, green or red, 



tt Frond dejinite. 



Gloeocapsa. Cells enclosed in wide gela- 

 tinous coats, enclosed in similar wide gela- 

 tinous parent coats for several generations 

 (PI. 7. figs. 4 & 13). 



Eotrydina. Frond globose, the peripheiy 

 composed of cells cohering into a kind of 

 cellular epidermis ; inner cells free (PI. 7. 

 fig. 9). 



Coccochloris. Frond gelatinous, globose, 

 containing numerous distinct cells, all free 

 (PI. 7. fig. 6). 



Clathrocgstis. Frond gelatinous, at first 

 globose, then hollow and broken into a 

 coarse net, crowded with minute cells (PI. 

 5. fig. 9). 



Meris77iopcedia. Frond very minute, flat, 

 sc^uare, containing cells in families of four, 

 sixteen, and sixty-four (PI. 7. fig. 12). 



Urococcus. Frond composed of striated 

 gelatinous tubes, formed of the parent cell- 

 membranes in a single row, with solitary 

 or binary cells in the ends (PI. 7. fig. 7). 



Hormospora. Frond a wide, gelatinous, 

 simple or branched sheath, containing a 

 single row of cells in twos or foiu-s (fig-. 33B, 

 p. 395). 



Tetraspora. Frond gelatino us, foliaceous ; 

 cells in fours, becoming free as zoospores 

 (PL 7. fig. 10).  



Hydrurus. Frond toughly gelatinous, 

 filiform, containing imbedded longitudinal 

 rows of cells (PI. 7. fig. 8). 



Pahnodictyon. Frond gelatinous, filiform, 

 branched; branches anastomosing into a net, 

 consisting of large vesicular cells, ^\•ith co- 

 loured contents which escape as zoospores. 



** Cells single, either solitary or united 

 in small numbers into families (Unicellular 

 Algae). 



Sckizochlamys. Cells free, globular, green, 

 aggregated in a jelly, each dividing into 2 

 or 4 portions, set free by the parent cell 

 breaking into 2 or 4 segments. 



ChJorosphcera. A large free globose cell, 

 with green contents, ultimately dividing 

 into two cells, each forming a new cell like 

 the parent, set free by lateral rupture (PI. 5. 

 %• 4). 



Characiunt. A minute attached, pyriform, 

 fusiform, or roimded, shortly stipitate sac 



