38 PLANT LIFE 



So far we have only considered aquatic 

 forms of algae, 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 



Fig. 4. Prasiola stipitata. I. General appearance of plant 

 magnified about four times. II. 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- 

 jduction is correlated with the change of 

 1 habitat from water to the land. The cells 

 which become detached from the frond are 



