20 Rhodora [FEBRUARY 
25 и; cells 5-20 diam. long, mostly somewhat clavate; often with a 
distinet annular constriction shortly above the lower end; branching 
mostly opposite below and.often above, but also often lateral, the short 
ramuli somewhat secund; branches and ramuli at first rather patent, 
soon curving upward; apex of terminal cell shortly conical with rounded 
tip.— Montego Bay, Jamaica, June 12, 1907. Collected by Dr. M. 
А. Howe, in connection with the expedition of the New York Botani- 
cal Garden to Jamaica. No. 4978. ‘Type material in herb. F. S. C. 
and herb. N. Y. B. G. 
In general appearance this species reminds one of a small and dense 
form of C. gracilis such as is often found in shallow pools on the north 
Atlantic coast, but the resemblance is merely external, the branching 
being more like that of C. rupestris, from which, however, it differs 
much in dimensions and texture. The cells vary in length, but aver- 
age quite long, and usually increase slightly in diameter from the base 
to the summit. In the older parts the branching is quite regularly 
opposite, and as the basal cells of each branch are of the same size 
as the cell of the main filament arising between them, the effect is 
that of trichotomy. In a few cases four practically similar cells have 
been seen arising from the same point. As a branch or a pair of 
branches arises from about every second cell of a filament, the frond 
becomes very derise, and as the development seems to go on quite uni- 
formly throughout the frond, the outline is usually regular. ‘The con- 
striction does not occur on all the cells, and may be more or less promi- 
nent; often it is very distinct, the diameter of the cell being reduced 
at this point to less than half the normal, the interior thickening of the 
cell wall contributing to the reduction. This constriction is interesting 
as showing a possible relation to the Valoniaceae, in which the char- 
acter is sometimes strongly developed. 
MALDEN, MASSACHUSETTS. 
EXPLANATION OF PLATE 78. 
Fig. 1, Cladophora Howei, portion of basal filament with erect branches. 
Fig. 2, microcladioides, portion of densely branching frond. 
Fig. 3, » “ general scheme of branching. 
Fig. 4, “ constricta, trichotomy in a main branch. 
Fig. 5, й Чч main branch, outline only. 
Fig. 6, “ graminea, end of branch, outline only. 
