410 



A TEXTBOOK OF BOTANY 



[On. X 



FIG. 280. Eu- 

 glena gracilis ; X 

 600. 



only in low degree, there is one special small group, called 

 Myxobacteriacece, probably developed from Bacteria, in 

 which the colony is somewhat highly de- 

 veloped, as illustrated in the typical form 

 herewith pictured (Fig. 279). 



CLASS 3. FLAGELLATA : THE FLAGELLATES 



These are minute free-swimming organ- 

 isms of fresh water, oftenest seen 

 when material from ponds is under the 

 microscope. Over 300 species are known. 



A typical form is Euglena gracilis, rep- 

 resented in Figure 280. The slender-elon- 

 gated unicellular body, free swimming by 

 aid of the terminal long flagellum, contains 

 nucleus, large chloroplasts, a vacuole which 

 Above is an adult is contractile, and a red pigment spot (or 

 individual showing eye _ spot ) which is sensitive to light, 



the very thin wall, J * 



the nucleus with toward which the Euglena ordinarily swims. 

 nucleoius the cy- Jt rep roduces by longitudinal fission, but 



toplasm, the elon- 

 gated chloroplasts, no sexual reproduction is yet known. In 

 the crescent-shaped autumn ft f orms a thick-walled resting 



red pigment spot 



(black), and, just sporewhich lastsover winter and germinates 

 above the latter, the th spr i ng e ach spore (in this case) 



contractile vacuole. 



The form pictured producing four new plants. While Euglena 

 is usual, but hke - g or( Ji nar iiy independent, making its own 



most x 1 lagellates 



Euglena readily food photosynthetically, it can also exist 

 Ob 5 n 5 8 * it 5 -! ha - pe in organic solutions as a saprophyte, under 



tinci tiiit oi its in 



terior parts. Below which condition it loses its chlorophyll. 



nation*" of* *& res-tin" ^6 CaSG * S ^ ' m ^ eres ^ as showing how 



spore. (After Zum- readily the saprophytic may originate from 



the independent habit. 



While Flagellates are typically unicellular, they often form 

 gelatinous colonies, which are either globular and free float- 

 ing, or attached and variously branched. Sometimes the 



