58 
Schrad. Cumberland (Blake). Port. Soc. Nat. Hist. Coll., No. 
100. Portland (Fuller). 
Family DICHAENACEAE. 
122. Dichaena Faginae (Pers.). On living beech. Cumberland 
(Blake). 
A new Oscillatoria from California. 
OSCILLATORIA TRAPEZOIDEA 0. sp. 
Trichomes aeruginous, forming a thin loosely-woven stratum 
of a dull blue-green color, firm, straight, 12-15 » in diameter, 
slightly attenuated and in most instances somewhat arcuate at the 
apices, provided with a delicate sheath; articulations 2 4-3" 
times shorter than the diameter, 4-6» long, with delicately 
granulose protoplasm, near the end of the filament prominently 
enlarged at the joints, giving, in sectional view, a somewhat trape- 
zoidal form to the secondary cells; apical cell pyramidal or con- 
ical, sometimes bluntly rounded, not capitate; no calyptra. 
Hab.: bottom of pond. Pasadena, California. Oc- _ 
tober, 1895. Collected by Prof. A. J. McClatchie. eS 
The hormogones are almost constantly arcuate at \ 
each end and, with few exceptions in opposite direc- 
tions, so that they may be said to be somewhat sigmoid 
in form. In the mature filaments this arcuate character 
is, however, not always present, at least at both ends. 
In the same way the degree of attenuation and the 
shape of the end of the filament may vary to a consid- 
erable ‘degree. Thus the apex may be globose or 
bulging, truncated, giving an almost square outline to 
the cell, or, going to the other extreme, it may be 
somewhat pointed, which is more common. 
The bulging character furnished by the ends of the 
mature cells near the extremity of the filament is con- 
stant and peculiar to the species so far as is known. 
One might represent such a cell by placing, base to 
base, two low glass beakers with flaring edges. The 
two flaring edges would then be the ends of the primary 
cell, while the line made by the bases of the beakers 
could be taken as the new cell-wall thrown across, separating the oo 
two secondary cells. “a Vee: 
