8 



THALLOPHYTA 



amoeboid changes of form may occur, but a true cell-wall is absent. They 

 are motile by means of one or more apical cilia each one being called a 

 flagellurn* . Green chloroplasts in the form of bands, plates or discs 

 may or may not be present, and therefore the nutrition of the plants may 

 be that typical of either the algae or the fungi. Reproduction takes place 

 only by simple division in the Longitudinal plane f. Each individual is however 

 capable of forming vesting cysts (see Fig. 3). The figure shows different 

 forms and stages of one of the commonest fresh-water forms called Euglena^ 

 also illustrated on Plate 2. 



Attention should be called to the peculiar vacuoles met with in these 

 plants, which alternately expand and collapse. They are found just behind 

 the flagella and are known as contractile vacuoles. 



V. CHLOROPHYCEAE. 



The Green Algae. 



The Chlorophyceae present the greatest diversity of form and structure, 

 ranging from minute, unicellular, motile forms to such plants as the "sea- 

 grasses" and Caulerpas (Fig. 4), the latter closely resembling in their external 



Fig. 4. Caulerpa crassifolia }. G. Agardh. Plant (a single cell), nat. size. a t dorsiventraJ 



apex of stem ; r, roots; /</', branches with distichous leaves. (After J. Sachs.) 



form some of the higher plants, but consisting of a single although much 

 branched cell. 



* C ilium : a hair ; flagellum : a whip. 



+ Reproduction hy means of (/dilutes forming :.//</otc,s also OCCUR in this group. The 

 process resembles in essentials that described on p. 9 under Sphaerella. See Fig. 3 C—F, 



