Howe: ALGAE OF BERMUDA AND THE BAHAMAS 355 
Protoderma (?) polyrhizum sp. nov. 
Thalli light green, irregular in outline, confluent or widely 
continuous, closely appressed and following the irregularities 
of the subs stratum, mos tly 2-10 cells thick, more or less uni- 
stratose at margins, showing frequently small ventral lobes and 
ridges penetrating and perhaps boring out minute cavities in 
the substratum; cells of the dorsal surface irregularly hexagonal 
or pentagonal in surface view, 10-24 w (mostly about 14 uw) in 
diameter, often somewhat longer at the margins, the separating 
walls firm, usually 1.5-4 py thick; cells of the interior and of the 
oe finally more or less branched, contorted or geniculate, 
mostly 6-20 p in diameter; unmodified cells of oe dorsal surface 
becoming sporangia, t these apparently of two kinds, one with 
very numerous and minute ovoid pallet pene Sta (?) about 
1 u. long, these (in dried plants) Haw lying in more or less coherent 
mucous masses on the surface of the emptied cells, other sporangia 
producing larger, ovoid, ellipsoid, or fusiform aplanospores 
(?) 2-4 w long. 
Forming a thin almost continuous green crust on an eroded 
oélitic or aeolian limestone pebble in a cavern, low littoral. 
Malcolm Road, Caicos Islands, Dec. 19, 1907 (Howe 5686, type), 
The rhizoids spring mostly from ridges or irregular ventral 
thickenings that fit into grooves or cavities of the substratum 
and they may be wholly lacking over wide areas of the smoother 
parts of the ventral surface. Wille (Eng. & Prantl, Nat. Pflan- 
zenfam. 12: Nachtr. 79. 1909) denies ‘“‘rhizoidenartigen Verz- 
weigungen”’ to the genus Protederma 
As compared with specimens of Protoderma marinum Reinsch 
from Achill Sound, Ireland, distributed by Mr. A. D. Cotton, 
the cells of the dorsal surface of the Bahama plant are much 
larger and are much more firmly and regularly parenchymatous 
in their general arrangement; and the same holds true when 
comparison is made with specimens from Massachusetts dis- 
tributed as P. marinum by Mr. F. S. Collins (Phyc. Bor.-Am. 
LIII), though the cells of the latter are larger than those of the 
Irish specimens, 
_ Chondrocystis Bracei sp. nov. 
Thallus cartilaginous or dinnaitden le pinkish blue-green 
when living, more or less incrusted with lime, forming irregular 
expansions about I.5 mm. broad | (or broader through coalescence), 
