1907] > Collins,— Some New Green Algae 199 
Filaments erect, straight, 12-20 » diam. at base, increasing in size 
upwards, to 35 y» in the upper part of the vegetative plant; lower cell 
up to 1 mm. long, next cell up to 10 diam. long, upper cells 2-3 diam.; 
walls thick; fertile cells in upper part of the filament, up to 50 x diam., 
1—4 diam. long, from slightly moniliform to nearly globular; zoospores 
escaping by an opening near the middle of the cell, through a very 
short tube; basal layer a dense mass of very irregular, pluricellular, 
coralloid branches, forming a dense and continuous expansion on the 
substratum. On the backs of the turtles, Chrysemys marginata and 
Aromochelys odorata, Walnut Lake, Oakland County, Michigan, Dr. 
T. L. Hankinson. 
Species of Chaetomorpha are abundant in all seas, but very unusual 
in fresh water, the only species which can be considered as well known 
being C. Herbipolenis Lagerh.,! which was found in a hothouse in a 
botanical garden, the place of its origin being unknown. C. Hen- 
ningsii Richter ? occurring in fresh water near Berlin, is uncomfortably 
near the marine C. aerea, which is said to be found occasionally in 
fresh water. The present species seems to be amply distinct from 
C. Herbipolensis, by the smaller diameter, longer basal cell, and espe- 
cially by the strongly developed basal layer, that of C. Herbipolensis 
being merely an outgrowth from the membrane, while in the present 
species there are distinctly branching, pluricellular filaments, which 
unite to form a practically continuous layer on the substratum, the 
shell of the turtle. The basal developments of the individual plants 
are so closely united that the appearance is that of a continuous mem- 
brane, from which arise numerous erect, bright green, straight fila- 
ments, pretty uniformly increasing in size from the base to the apex. 
The cell wall is thick, in the lower cell about one quarter the diameter; 
the cells in the vegetative filaments are nearly cylindrical, but the 
fertile cells are strongly swollen, sometimes nearly globular. ‘The 
material examined having been preserved in formalin, nothing can be 
said as to the finer details of the zoospores, but evidently large numbers 
are formed in a cell. Emptied cells showed plainly an aperture near 
the middle, the cell wall extending as a very short tube, much like 
that shown for C. Herbipolensis, Pl. IX, fig. 5. Two lots of material 
were received from Dr. Hankinson, one having grown on Chrysemys, 
the other on Aromachys; there was some difference between the two, 
the former having basal cells longer and more slender than the latter, 
and fertile cells more distinctly swollen. 
1 G. Lagerheim, Ueber die Süsswasser-Arten der Gattung Chaetomorpha Kütz. Ber. 
Deutsch. Bot. Ges., Vol. V, p. 185, 1887. 
2 P, Richter, Hedwigia, Vol. p. 70, 1893. 
