FOUNDATIONS 17 



separated in our minds into the two kingdoms of plants and 

 animals respectively. 



The animal kingdom is divided into two sub-kingdoms 

 or phyla, the protozoa and the metazoa. Botany has no 

 group that corresponds exactly to protozoa, indicating a 

 division in which the greatest structural differentiation is 

 reached in unicellular bionts. The term protophyta was 

 used by Sachs to denote a joint group of algae and fungi ; 

 blue-green algae (Cyanophyceae) like Chroococcus, Nostoc, 

 &c., and green algae (Chlorophyceae) such as Pleurococcus ; 

 together with the bacteria and yeast-fungi. 



The Thallophyta in botany are a section of the cryptogams, 

 and include all plants lower in organisation than the mosses. 



The body of such plants is termed the thallus (Gr.^green 

 bough). The vegetable protists include Sachs's Protophyta 

 and filamentous algae such as the Ulotricheae, the Conjuga- 

 teae (Zygnemieae, desmids, and diatoms), and others such 

 as Vaucheria, which produce oospores, together with the 

 corresponding fungi, Phycomycetes, and a number of other 

 groups of algae and fungi. The commoner grouping of 

 organisms in descending scale is into classes, orders, genera, 

 and species ; secondary groups being intercalated as affinities 

 require. The terms genus and species as defined by 

 Linnaeus are unchangeable ; as regards the remainder 

 custom varies with different authors, but the terms class and 

 order are fairly constant in application. 



In botany names of orders are Latin adjectives ending 



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