330 



THALLOPHYTES 



plant and animal kingdoms. The protoplast is naked or in- 

 vested by a membrane which usually contains no cellulose. 

 They are commonly abundant in stagnant water and among 

 Green Algae some are usually present. 



Euglena represented in Figure 284 is one of the most common 

 of the 300 or more species and will serve to show the structure 

 and habits of the group. Euglena is quite commonly seen 



.swimming about under the 

 microscope when Algae are be- 

 ing examined. The slender 

 unicellular body bears a long 

 terminal flagellum, has a chlo- 

 roplast, eye-spot, and pulsating 

 vacuole. These structures are 

 characteristic of the Algae, 

 such as Volvocales and also of 

 protozoa, the one-celled ani- 

 mals. No sexuality is known, 

 and multiplication is effected 

 by longitudinal fission, a 

 method characteristic of the 

 lower animals. At the ap- 

 proach of unfavorable condi- 

 tions, as in autumn, it trans- 

 forms itself into a thick-walled 

 resting spore which germinates 

 and produces one or more new 

 plants when favorable condi- 

 tions return. Although it 



FIG. 284. A common species of 

 Euglena (Euglena gracilis). At the 

 left, an adult individual, showing the 

 flagellum, the pulsating vacuole (p), 

 the chloroplast (c), and the nucleus 

 (n) ( X 650) ; at the right and below, 

 Euglena in the spore stage (X 1000); 

 at the right and above, a spore germi- 

 nating and producing four new indi- 

 viduals (X 1000). Redrawn from 

 Zumstein. 



usually makes its own food, 

 sometimes Euglena loses its 



chlorophyll and lives on organic solutions as a saprophyte, thus 

 demonstrating that the saprophytic may readily originate from 

 the independent habit. 



Many of the Flagellates change their forms readily like the 

 Amoeba. Sometimes the individuals form colonies of various 

 shapes and often variously branched. 



Such features as the possession of chlorophyll and the forma- 

 tion of thick-walled resting spores suggest a relationship of the 

 Flagellates to plants, while their swimming habits, amoeboid 



