132 University of California Publications in Botany [Vol. 6 



not have to endure so much cold. Taking the distribution according 

 to summer temperatures, the following statements as to the relation of 

 the occurrence (so far as known) to isotheres may be of interest. 

 Between isotheres 10°-15° C possibly two species may be found, viz. : 

 Scinaia furcellata and GloiopJiloea confusa, but probably always nearer 

 the 15° C than the 10° C line. Six species, viz., Scinaia furcellata, 

 8. moniliformis, Gloiophloea Scinaiodes, G. undulata, G. confusa, and 

 Pseudoscinaia australis, are to be found between the isotheres of 15° 

 and 20° C, while between the isotheres of 20° to 25° C are to be found 

 eleven species, viz. : Scinaia furcellata, S. Johnstoniae, S. japonica, S. 

 latifrons, S. Cottonii, S. Salicornioides, S. articulata, Gloiophloea 

 Okamurai, G. capensis, G. confusa, and Pseudoscinaia Snyderae. 

 These are subtropical species. The tropical species occurring between 

 the isotheres of 25° and 30° are five, viz., Scinaia Johnstoniae, S. com- 

 planata, S. Iwrnioides, S. carnosa, and Gloiophloea Halliae. The true 

 tropical species is S. carnosa because it lives constantly in tropical 

 heat; Scinaia hormoides is at times subject to a temperature of 23°- 

 24° C. Scinaia complanata and Gloiophloea Halliae have about the 

 same temperature relations as Scinaia hormoides, while Scinaia John- 

 stoniae endures much colder waters still (winter temperature as low 

 as 14° C at least). 



The Scinaia assemblage, then belongs to the warmer waters, mostly 

 being the subtropical waters (20°-25° C) and entirely absent from 

 the colder waters. They may be contrasted with the other members 

 of the Chaetangiaceae. The species of Galaxaura are all tropical, or 

 at least very nearly so. The single species attributed to Actinotrichia, 

 while widespread, is, however, strictly tropical. The ill understood 

 genus Chaetangium has ten species, only one of which is tropical. 

 Three of these species, however, are subtropical, i.e., inhabiting waters 

 between 20-25° C. Four species are credited with inhabiting waters 

 between 15° and 20° C, and the other two with inhabiting waters 

 between 5° and 10° C. 



While the temperature of the water has the absorbing interest as 

 presumably regulating and restricting the limits of the particular 

 distribution of the species, there are certain general facts of distribu- 

 tion which are generally emphasized and which, also, are usually looked 

 upon as throwing light upon the origin and spread of the various 

 members of such a group as the Scinaia assemblage. 



In the European-East North American region, viz., the North 

 Atlantic, are to be found two (possibly three) species, viz., Scinaia 



