SCHIZOGONIUM. 139 



filament of one row of cells may be changed to a filament 

 of more rows ; in the mass some had two, some four, some 

 eight rows of cells. Comparing with good specimens of 

 European Prasiola crispa, as contained in Wittr. and Nord.'s 

 Algae Exsiccatae, No. 47, filaments with a single row of cells 

 occur which are in perfect harmony with mine ; these divide 

 longitudinally, producing threads with two rows of cells, of 

 four, of eight and so on until a leaf-like frond is produced- 

 the matured Prasiola. Having had no opportunity to 

 examine specimens of other collections, the question may 

 reasonably be asked, is not the plant an undeveloped form 

 of Prasiola, rather than an Ulothrix ? 



There is some analogy between this form and Schizogonium, 

 but this is an air (exposed rock) plant, mine a water plant. 



Genus 26, SCHIZOGONIUM, Kg. 



* 



Filaments as in Ulothrix, more or less laterally connate, (dupli- 

 cate or triplicate) or by cellular division in two directions form- 

 ing narrow flat bands which are somewhat crispate. 



The relation between Schizogonmm, Ulothrix, and Prasiola is 

 close and in some stages of development they do not admit of 

 separation. As a rule UlotJirix is composed of simple filaments, 

 with one row of cells ; Schizogonium has two or more filaments 

 connate ; and Prasiola is frondose. The opinion has been ex- 

 pressed that Ulotlirix is the young stage of growth ; Schizogonium a 

 more advanced condition with collateral segmentation, and 

 Prasiola the adult stage. However appearances may sometimes 

 favor such opinion, am not yet convinced, nor ready to accept. 



SCHIZOGONIUM MURALE, Kg. 



Dark green, forming a broadly expanded, soft, velvety 

 stratum ; threads sometimes free, sometimes two or three 

 laterally united 5 cells 2-4 times shorter than the diameter, 

 pectinate, often crowded, sometimes interrupted ; cell-mem- 

 brane rather thick, colorless, slightly undulate and con- 

 stricted. 



Diameter of filaments, 15-18 //. 



Moist cliffs, Colorado; the only good specimens hitherto 

 observed. 



Plate CXIX, figs. 16-18. 



