Structure of Spongocladia , A resch . 1 7 1 
successive cells, their insertion being sometimes at the 
upper end, as in Cladophora , or the middle. At times, 
however, the diameter of a branch is nearly as great as the 
length of the cell from which it takes its origin. The lateral 
branches, which are sometimes again branched irregularly, 
probably serve to bind more closely together the interwoven 
filaments. This function is more effectually performed by 
certain other branches which become permanently attached 
to the surface of adjacent tubes by numerous, short, rhizoid 
processes. This possibly explains the anastomosing described 
by Zanardini. Above the septate portion of the filament 
Fig. 9. Portion of filament of Spongo - Fig. 10. Zoospores of Spongocladia 
cladia vaucheriaeformis , showing obli- vaucheriaeformis germinating in situ 
teration of lumen. (after Areschoug). 
there is commonly found one cell longer than the others, and 
above that again the main portion of the tube — the terminal 
cell — of great length without cross-partition of any kind, and 
very closely resembling in this respect as well as in its com- 
paratively great diameter, and the nature of its contents, 
the tubes of a Vaucheria. Throughout the course of the 
tube it is much wrinkled lengthwise. Some of the wrinkling 
is probably due to drying, but there are also finer markings 
which seem to represent fibrillar thickening of the cell-wall. 
This structure is seen when a filament has been broken by 
stretching, and fine threads are left projecting from the 
broken edge. Areschoug’s figure 5 shows the cell-wall re- 
