378 



BOTANY 



I- ART II 



substratum and are both phototactic and cheniotactic. These movements 

 are effected by the swelling of an anisotropous mucilage excreted by the cells. 

 The main axis of swelling of this forms an acute angle with the long axis of the 

 filament, so that the latter is moved forwards without rotating on its axis( IO ). 



Some Cyanophyceae take part with the Fungi in the formation of Lichens. 

 Some species also are endophytic and inhabit cavities in other plants, e.g. 

 Anabaena in Azolla, Nostoe in some Liverworts, in Lemna, and in the roots of 

 Cycas. Nostoe punctiforme occurs as a facultative parasite in the rhizome of 

 Gunner a ( 106 ). 



CLASS III 



Flagellata (Flagellates) ( 



The Flagellata are a group of unicellular, aquatic organisms 

 exhibiting a wide range of form ; they combine animal and vegetable 

 characteristics, and may be regarded 

 as the starting-point on the one side 

 of unicellular Thallophytes, on the 

 other of the Protozoa. 



The protoplast exhibits con- ' 

 tractile or amoeboid movements, and 

 is limited by a denser protoplasmic 

 layer and not by a definite cell 

 wall. One or more cilia (flagella) 

 are present as motile organs. The 



Fio. 303. Chrysamoeba radians. Occurs in fresh 

 water und has a single cilinm and two brown- 

 ish-yellow chromatophores. 1, Ordinary form ; Fn;. 3U4. Diuobryon Sertuhma. Occurs in 

 2, amoeboid condition with radiating pseudo- fresh-water plankton and forms invested 

 podia. (After KLEBS.) colonies, (x 600. After SENN.) 



protoplast contains a nucleus, a pulsating vacuole, and in many species 

 well -formed green, yellow, or brownish -yellow chromatophores. A 

 red eye -spot is frequently present. The assimilation product is 

 usually oil, but starch and other carbohydrates also occur. Other forms 

 are colourless and are saprophytic or obtain their food like animals. 

 The protoplast of some Flagellates, especially of the colourless forms, 



