38 PLANT LIFE 
So far we have only considered aquatic 
forms of alge, but there are certain kinds 
which grow in damp situations on land. 
Amongst these is Prasiola, which is not un- 
frequent in certain localities (Fig. 4). Its body 
is composed of a leaf-like expansion of cells 
which lower down form a contracted stalk-like 
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Fig. 4.—Prasiola stipitata. 1.—General appearance of plant 
magnified about four times. I1.—Portion of frond magni- 
fied 300. The living cell contents are embedded in the 
flattened jelly which originates by the swelling and growth 
of the cell walls. 
body attached to the soil by means of special 
filamentously elongated: cells called rhizoids. 
The cells which compose the substance of the 
thin leaf-like body are all alike, but the 
common walls, as befits a terrestrial organism, 
are more cartilaginous and tough than those 
of the more aquatic types. Even repro- 
duction is correlated with the change of 
‘habitat from water to the land. The cells 
which become detached from the frond are 
