THE GEOLOGIC FUNCTIONS OF LIFE. 



653 



good record of their life. Nevertheless all the great groups of plants, 

 viz. the Thallophytes (algae, fungi), the Bryophytes (mosses, liver- 

 worts), the Pteridophytes (ferns, horsetails, lycopods), and the Sper- 

 matophytes (gymnosperms, angiosperms) have left some record. 



REFERENCE TABLE OF THE PRINCIPAL GROUPS OF PLANTS. 



Thallophytes 

 (Thallus plants) 



Algae and algoid 

 forms 



Fungi and 

 fungoid forms 



Bhyophytes 



(Moss plants) 



Pteridophytes 

 (Fern plants) 



Lichens 

 j Hepaticae, liverworts, 

 i' Musci, moss6s. 



Cyanophycese, blue-green algse. 

 Chlorophyceae, green algse. 

 Rhodophycese, red algae, 

 Phaeophyceae, brown algae. 

 Diatomaceae, diatoms. 



. Charophyta, stoneworts, 



' Phycomycetes, algae-fungi, water-molds. 



Ascomycetes, ascus-fungi, mildews. 



Basidiomycetes, basidium-fungi, mushrooms. 



^Ecidiomycetes, aecidium-fungi, "rusts." 



Schizomycetes, ''fission-fungi," bacteria. 

 . Myxomycetes, "animal fungi," slime-molds. 



Symbiont algae and fungi. 



Spermatophytes 

 (Seed plants) 



Filicales 



Equisetales 

 Sphenophyllales. 



Lycopodiales 



Filices, true ferns. 

 Cycadofilices, cycad-ferns. 

 Equisetse, scouring-rushes, horsetails. 

 Calamites. 



I Lycopodiaceae, club-mosses. 

 ^ Lepidodendra. 

 ( Sigillaria and stigmaria. 

 Cordaiteae 



Gymnospermae 

 (Naked seed) 



Angiospermae 

 (Covered seed) 

 (Flowering 

 plants) 



cordaites. 

 Cycadales \ Bennettiteae. 



(cycads) ] Cycadaceae. 

 Coniferae, evergreens. 

 . Ginkgoaceae, ginkgo. 

 ' Monocotyledoneae, cereals, grasses, etc. 

 (one-leafed seed). 

 Dicotyledonese, oaks, poplars, peas, etc, 

 (two-leafed seed). 

 The contribution of the Thallophytes (algae, fungi, bacteria). — The 



Thallophytes embrace the simplest types of plants, and are probably 



the nearest present representatives of the ancestral forms. Some of 



them are minute one-celled organisms, as simple as an organism can 



well be conceived to be. The simple blue-green algse of our fresh waters 



well represent this class. The most are, however, multicellular, and some 



(as the great seaweeds) rise to a degree of complexity and of a bodily 



segmentation resembhng that of the higher plants. The various species 



are adapted to an extremely wide range of conditions; some live in hot 



springs at 170° Fahr., and some in Arctic seas at the freezing-point; 



some flourish in fresh water, some in brackish, some in salt water, 



and some even out of the water. This wide adaptation implies an 



