444 University of California Piihlications in Botany [Vol. 6 



This species is placed in the melius Hyella on account of its close 

 similarity in some of its vegetative characters and its penetrating- 

 habit to those of //. cacspitosa Bornet and Flahault (1888), the orig- 

 inal species of the genus. They represent cell divisions as taking 

 place in all directions at the base of the erect filaments. In surface 

 view the cells arising from divisions of the cells in the basal filaments 

 appear in more or less isolated groups in their illustrations. The few 

 cells near the base of the erect filaments are less divided, and the 

 terminal cells of the erect filaments remain undivided. The erect 

 filaments thus become somewhat isolated, and clavate in form. The 

 filaments of H. sociaUs appear to be formed in the same manner as 

 those described and figured by Bornet and Flahault, although they 

 are crooked and branched. In the absence of knowledge concerning 

 the prostrate portion of the thallus, characteristic of typical Hyella, 

 and in the absence of gonidangia, this species must remain in doubt 

 as to its generic position. 



Radaisia laminariae Setchell et Gardner sp. nov. 



Plate 37, figs. 14-16 



Thallo prostrato filamentis compactis radiantibusque, dichotome 

 aut subdichotome ramosis, stricte compacto, orbiculari, ad 300^ diam. : 

 cellulis filamentorum prostratorum quadratis, 4-4. 5/x diam., per par- 

 titiones horizontales filamenta compacta erectaque producentibus ; 

 thallo adulto 30-40/x crasso ; gonidangiis in filamentis erectis termin- 

 alibus, sphericis aut lente ovalibus, 8-9/x diam. ; gonidiis 0.8/a diam., 

 partitione simultanea ; thallo laete caeruleo-viridi. 



Prostrate portion of the plant consisting of compact, radiating 

 filaments, dichotomously or subdichotomously branched, forming a 

 closely compact thallus circular in outline, up to ^QQ/x diam. ; cells of 

 prostrate filaments quadrate, 4-4.5/tx diam., giving rise by horizontal 

 divisions to closel.y compact, erect filaments ; the whole thallus 30-4()iU. 

 thick; gonidangia terminal on the erect filaments, spherical, or slightly 

 oval, 8-9/A diam. ; gonidia O.Sjn diam. formed by simultaneous division ; 

 color bright blue-green. 



Growing on the terminal portion of the blades of Laminaria 

 Sinelmrii. Fort Point, San Francisco, California. This locality is, 

 so far as I know, the only one in which this species has been observed. 

 It probably has a much wider distribution. The host plant extends 

 from the vicinity of Point Conception. California, to Vancouver 

 Island. 



T have presented a brief discussion in the introduction to this work, 

 page 430, in r(>gard to the relation between the general Hyella and 

 Radmsia. R. laminariae I have taken to represent a typical species 



