342 



BOTANY 



PAKT II 



regarded as tlie starting-point on the one side of unicellular Tliallophytes, on the 

 other of the Protozoa. 



The protoplast exhibits contractile or amoeboid movements, and is limited 

 by a denser protoplasmic layer and not by a definite cell wall. One or more 



organs. The protoplast contains a 

 nucleus, a pulsating vacuole, and in 

 many species •well - formed green, 



cilia 



(flagella) are present as motile 

 ^ th 



-It 



Pio. 254. — Eugtena gracilis. A, Form with green 

 chroinatopliores (ch) ; n, nucleus ; v, vacuole and 

 red eye-si)Ot ; g, flagellum. B, Henii-saprophytic 

 form with small green chroraatophores. C, 

 Colourless saprophytic form occurring in nutrient 

 solution in absence of liglit. D, Resting cyst of 

 the form C ; r, red eye-spot. E, Germination of 

 the resting cyst of the form A by di\-ision into 

 four daughter cells which later escape. (After 

 ZUMSTEIN ; A,C, X 630 ; B, x 050; D, E, x ICOO.) 



yellow, or brownish-yellow chromato- 

 phores. A red eye-spot is frequently 

 present. Other forms are colourless 

 and live saprophytically ; many are 

 also able to take u]) solid particles as 

 food. 



Most representatives of the group 

 live as naked, free cells ; others form 

 more or less complicated cell-coloiries 

 held together by mucilage, or they 

 possess peculiar stalked or unstalked 

 lirm investments. 



Sexual reproduction is wanting. 

 Multiplication takes place by longi- 

 tudinal division, and in many species 

 thick-walled resting spores or cysts 

 are produced. 



Euglena (Fig. 254) may be taken 

 as an example. The species live in 

 water containing organic substances 

 and often appear in large numbers. 

 By varying the nutritive conditions 

 colourless forms with reduced chro- 

 matophores are obtained (^**). 



Class IV 



Myxomycetes (Slime-Fung-i) 



The Myxomycetes form an 

 independent group of lower 

 Thallophytes ; in certain respects they occujjy an intermediate position 

 between plants and animals, and have in consequence also been termed 

 Mycetozoa or Fungus-animals. They are represented by numerous 

 species, and are widely distributed over the whole earth. In their 

 vegetative condition the Slime-Fungi consist of naked masses of proto- 

 plasm, the PLASMODIA, containing numerous small nuclei but utterly 

 devoid of chlorophyll. Glycogen occurs as a reserve substance, while 

 starch is not found. The plasmodia (p. 54) ai'e found most frequently 

 in woods, upon soil rich in humus, upon fallen leaves, and in decaying 

 wood. They creep about on the substrata, changing their form at the 

 same time, and thrust out processes or pseudopodia, which may in 



