1918] Gardner: Xew Pacific Coast Marine Algae HI 471 



gi'latiiious and aiuorplious, in having fewer trichomes within the 

 sheath, and in the trichomes being larger and the cells much shorter. 

 From tile latter it ditl'ers in having smaller trichomes with shorter 

 cells, in not having the ends long attenuated and very acute-conical 

 as has that species according to the figures and descriptions given by 

 Crouan. The trichomes in M. Weeksii begin to taper about 6 to 10 

 cells back of the apex. 



Microcoleus confluens Setchell et Gardner s]x nov. 

 Plate 40, fig. 25 



Filis erectis, strata coeruleo-viridia, com])acta, spongiosa ad saxa 

 indefinite expansa formantibus ; vaginis gelatinosis. moderate amplis, 

 superficie irregularibus. hyalinis, homogeneis, primo distinctis aut 

 demum diffluentibus; trichomatibus in vaginis 1-8, distinctis aut laxe 

 intricatis : levissime ad dissepimenta constrictis, 4-4. o/a diam., rectis 

 et ad apices non attenuatis; eellulis 2-4-plo brevioribus, cytioplasmate 

 homogeneo ; cellula apicali moderate rotundata, membrana apicali 

 leviter incrassata. 



Filaments erect, forming a blue-green, compact, spongy stratum of 

 indefinite expansion on rocks ; sheath gelatinous, moderately ample, 

 irregular on the surface, hyaline, homogeneous, distinct at first or 

 later diffluent ; trichomes 1-8 in a sheath, separate or loosely entwined, 

 very slightly constricted at the dissepiments, 4-4.5/x diam., straight and 

 not attenuated at the apices ; cells 2-4 times shorter than the diameter, 

 protoplast homogeneous; apical cell moderately rounded, end wall 

 slightly thickened. 



Forming a spongy stratuni in comj)any witli other s])e('ies of 

 Myxophyceae on rocks in the upper part of the littoral belt. Lands 

 End, San Francisco, California. Type no. 1641, Gardner. 



The species of the genera Microcoleus and Hydrocoleum inter- 

 grade. Microcoleus is the older of the two genera having been estab- 

 lished by Desmazieres in 1823, based upon Canferva chthonoplastes 

 ]\Iertens {in Ilornemann, Flora Danica, 1818, tab. 1485). Kuetzing 

 established Hydrocoleum in 1843 (p. 196), and transferred to the 

 genus his Vaginaria saxicola and V. racomitrii. The forms upon 

 which each genus were originally founded are quite distinct. Typical 

 Microcoleus includes forms with numerous tightly entwined trichomes 

 within firm, fairly regular unbranched sheaths. The trichomes are 

 usually small, more or less pointed at the ends, mostly ranging below 

 lix in diameter, except M. subtorulosus which is 6-10^ in diameter, and 

 the cells are generally longer than the diameter. 



The majority of the species which have thus far been placed in 

 Hydrocoleum have fewer trichomes in a sheath, which is often more 



