PROTOCOCCUS. 



[ 539 ] 



PROTOMYCES. 



includes those unicellular Palmellaceae which 

 increase in the vegetative way by division 

 into two or four parts, which then become 

 more or less separated, but may remain con- 

 nected in irregular groups by a very sparing 

 semigelatinous layer resulting from the de- 

 composition of the walls of the parent-cell 

 (PL 3. fig. 2) : in addition to this, the contents 

 of the cells under certain circumstances 

 become divided into two or four isolated 

 portions (c), which are released by the solu- 

 tion of the parent-cell in the form of ciliated 

 zoospores (b, e, f), which, after a short 

 period of motion (during w r hich they some- 

 times divide again), settle down and produce 

 a cellulose coat, and then pursue the vege- 

 tative course of reproduction (fig. 613, page 

 536). It appears that smaller zoospores 

 (MICROSPORES) are sometimes formed in 

 great numbers (a), and set free in the same 

 way ; the fate of these is unknown. The 

 zoospores are produced in water ; when this 

 is dried up gradually, the vegetative cells 

 become converted into a kind of resting 

 spore, acquiring a thick coat, the contents 

 mostly turning from green to red (d). When 

 placed in favourable circumstances, these 

 resting forms (even after several years) 

 recommence the course of vegetation, re- 

 acquiring the green colour by degrees, in 

 the course of several generations of vegeta- 

 tive cells. The contents of the red form 

 appear to consist partly of oil-globules ; in 

 the green form the protoplasmic substance 

 is coloured by chlorophyll, and at a certain 

 stage contains starch. 



We have traced P. viridis through all 

 these stages, as represented in PL 3. fig. 2 

 a-g : a most elaborate monograph of P. plu- 

 vialis has been written by Cohn, which is far 

 too extensive to be analysed here, but goes 

 to establish the same conclusions, that the 

 genus Hcematococcus is founded on states of 

 Protococcus. The P. viridis of our figures 

 is undoubtedly a Chlamydomonas, one of 

 Ehrenberg's genera of Polygastrica, synony- 

 mous with Diselmis, Dujardin. This form 

 appears at first sight nearly allied to Euglena, 

 but there are striking differences in the 

 appearance and movements of the active 

 forms, and the "vegetative" forms are 

 somewhat different. It may be remarked, 

 however, that the zoospores of Protococcus 

 viridis, allowed to dry upon a slider, often 

 turn red and look just like small Astasice 

 (PL 3. fig. 2 g). 



We have remarked under PALMELLA, 

 that the Polar red snow appears to be a 



Palmella (PL 3. fig. 3d), although this 

 species has been called Protococcus and Hce- 

 matococcus nivalis ; and it appears to us that 

 Shuttleworth and others have confounded 

 this with Protococcus pluvialis. Hassall's 

 species of Hcematococcus, nos. 8 to 19, with 

 the exception of H. vulgaris ( Cklorococcum) 

 (PL 3. fig. 1), are probably congeneric with 

 our P. viridis. We find it impossible to 

 extricate the British forms from their con- 

 fusion ; the Palmellacea3 require a thorough 

 study in a living state. Meneghini's defini- 

 tions of the genera will not hold, and Kiitzing 

 has multiplied species to infinity. 



Our P. viridis makes its appearance com- 

 monly on damp earth, sand, &c., forming a 

 greenish coat of no perceptible thickness, 

 and the zoospores (Chlamydomonas) occur 

 constantly in standing pools in spring and 

 autumn, tinging the surface of the water 

 bright green, and as they settle to rest, form- 

 ing a kind of green scum at the margins (con- 

 stituting the green matter of Priestley). Cells 

 of resting form 1-2400" in diameter. P.plu- 

 vialis colours water red in like manner ; it 

 occurs on mountains, especially in melted 

 snow-water. Cells of resting form 1-1250 

 to 1-625" in diameter. Similar colorations, 

 however, are produced by various other 

 organisms (see WATER). 



It may be observed, that when the active 

 forms of P. viridis and P. pluvialis divide 

 without coming to rest, they produce forms 

 which are undistinguishable from many of 

 Ehrenberg's species of Polygastrica. When 

 they acquire a loose cellulose coat before 

 losing their cilia, they represent Gyges-, at 

 other times they resemble Chlorogonium, 

 Uvella, Polytoma, Monas, Bodo, &c. 



BIBL. Harvey, Brit. Alg. 1 ed. p. 180; 

 Hassall, Brit. Fr. Alg. p. 321, &c., pis. 76- 

 82 ; Meneghini, Trans. Turin Acad. 2 ser. 

 v. p. 1 ; Cohn, Nova Acta, xxii. p. 605 

 (abstr. in Ray Soc. Vol. 1853. p. 514) ; Von 

 Flotow, Nova Acta, xx. p. 414 ; Alex. Braun, 

 Verjungung, fyc. (Ray Soc. Vol. 1853. p. 206 

 et seq.) ; Nageli, Einzelliger Algen, passim ; 

 Kiitzing, Spec. Alg. p. 196, Tab. Phyc. i. 

 pis. 1-6. See also under RED SNOW. 



PROTOMYCES, Unger. A genus of 

 Ustilagines (Coniomycetous Fungi), growing 

 in the intercellular passages of leaves and 

 leaf-stalks. According to De Bary, these 

 Fungi consist of ramified filaments creeping 

 between the cells of soft tissues, and swelling 

 up at intervals (apparently where they meet 

 an intercellular space large enough), to form 

 globular spores: a filament with several 



