Notes . 367 
but little knowledge of the manner in which these rhizoids are produced, and of the 
conditions which determine their formation. 
The present note relates to a specimen of Spirogyra which has not yet been 
observed in a fertile condition, but which closely resembles S. adnata , and which 
will be provisionally referred to that species. The material was found as small tufts 
of bright green filaments attached to a log, which was completely submerged in the 
running water of a chain of ponds in the neighbourhood of Hampstead Heath. The 
sterile filaments appeared in July, 1912, and persisted until late in January, 1913, 
with somewhat variable algal associates, consisting of Vaucheria and Cladophora 
in the summer and autumn, and of Draparnaldia during the winter months. 
Fig. i. Spirogyra adnata (?). A. Typical assimilating cell with three chromatophores : pyre- 
noids only shown as seen at upper focus : position of lower chromatophores indicated by dotted lines : 
nucleus omitted, b. Lower part of filament dissected from log, showing assimilating cell (a), basal 
cells (p ), with rhizoids ( r ) bearing haptophores (Jt ), o which the broken ends only are seen : cell- 
contents omitted. 
No conjugation has been seen, although the spot has been under constant 
observation. 
The cells of the filaments vary from about 4.0 to 45 ju, in diameter, and are from 
one to three times as long as they are broad. The longest cells are those which are 
about to undergo division, in the upper part, or which bear rhizoids, in the lower part 
of the filaments. There are usually three chromatophores, with a slightly crenate 
edge, and with very small distant pyrenoids ; but four or even five may occur. In 
the assimilating cells, the chromatophores are closely set, each one making three or 
four turns (Fig. 1 a), but in the basal and attaching cells they are loosely arranged, 
or nearly straight, especially in the neighbourhood of the rhizoids (Fig. 2). The 
cell-walls are stout and often distinctly lamellose in the lower cells (Fig. 1 b). 
By teasing out the filaments from their woody base, it may be seen that the 
lower cells are elongated, with irregular and often nearly colourless plastids. They 
