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CHAPTER LXV. 



ALGsE AND FUNGI. 



The plants included in the great series of the Thattophyta are 

 separable into the two primary divisions of the Algce and Fungi, 

 and are characterised by the fact that they are composed of cells, 

 without true vascular tissue. They may be either unicellular or 

 multicellular, the organism in the latter case forming an expansion 

 or " thallus " which is not differentiated into stem, leaf, and root. 

 In the lower Thallophytes reproduction may be wholly non-sexual : 

 but in the higher forms sexual reproduction takes place, the result 

 being the formation of a spore, or a group of spores, or a fructifica- 

 tion within which spores are produced. 



Series I. Alce. — The group of the Algce includes unicellular 

 or multicellular Thallophytes in which chlorophyll is developed in 

 larger or smaller quantity. They vary extremely in form, and are 

 for the most part inhabitants of water, both fresh and salt. The 

 Alga may be divided into the following six classes, viz. : — 



Class I. Diatomaceae . . . Diatoms. 



Desmids. 



Brown Sea-weeds. 



Cymopolia, &c. 



Red Sea-weeds, Nullipores. 



Chara and Nitella. 

 I 

 As regards the general distribution of the Algce in time, many 

 forms are quite incapable of preservation as fossils, while others can 

 only be preserved under specially favourable circumstances. In 

 certain groups, however, the organism may secrete a siliceous en- 

 velope, or its tissues may undergo calcification, while others become 

 encrusted with carbonate of lime. Such forms readily admit of 

 petrifaction, and unquestionable remains of these occur in the fossil 

 state. Apart from these undoubted fossil Algce, numerous markings 



I. 



Diatomaceae . 



II. 

 III. 



Phycochromophycae 

 Fucaceae 



IV. 

 V. 



Chlorosporeae 

 Florideae . 



VI. 



Characeae 



