514 Piercy . — The Structure and Mode of Life of a 
terrestrial Algae to their conditions of life, the present observations were 
made on a form of Hormidium flaccidum . 
The results set out below relate to one form of this species occupying 
the bare stretches of a piece of grassland near a pond at Woodford, Epping 
Forest. The characteristic features of the Alga may be summarized as 
follows: The filaments normally consist of a single row of cells (Fig. 1, A) 
and may be of considerable length (including sometimes as many as 1,400 
cells) ; their width varies between 9 /x and 13/x, the average obtained from 
a large number of filaments being 11 /x. The lengths of the cells range from 
Fig. 1. A, portion of a typical filament of the Woodford form of Hormidium flaccidum growing 
on damp soil. B, cell containing two polar vacuoles. C, cell containing several small vacuoles in 
place of one of the polar vacuoles. D, e, parts of filaments showing abnormal cell-divisions. 
n., nucleus; ck., chloroplast; py., pyrenoid ; v., vacuole; st., starch; g., granule; d., dead cell. 
(A X 650 ; B X 2,000 : C, D X 1,200 ; E X 850.) 
two-thirds to two and a half times their width. A single plate-shaped 
chloroplast of a bright green colour lies just within the longitudinal wall of 
each cell, extending nearly the entire length and over about two-thirds of 
the circumference (Fig. i, A) ; one or both of its longitudinal edges have 
frequently a curved outline (Fig. i, c). The nucleus (Fig. i, A, n.) lies near 
to the longitudinal wall, usually between the two edges of the chloroplast. 
There are often two large vacuoles in each cell, extending a variable distance 
from the ends towards the middle (Fig. i, B, v . ; Fig. 4, n) ; in short cells 
there is occasionally only one vacuole traversing the whole length of the 
cell. Numerous small vacuoles may replace the larger ones (Fig. i, c). 
