Evolution of Vef/etul Life. 123 



triiuent \\\w\\ Avhicli the plant subsists. Among the fungi 

 are the bacteria, the yeast-plants, the bread-moulds, the 

 cheese-moulds, mushrooms, toadstools, rust, smut, and a 

 vast number of others of a related character. These, as is 

 the case ^vith most of the lower forms of life, multiply with 

 enormous rapidity. Together, the algae,- fungi and li- 

 chens form the sub-kingdom called Thallophyta, the charac- 

 teristic of Avhich is that the plants are without distinct dif- 

 erentiation of root, stem and lateral aj)pendages. 



Another sub-kingdom, — Cormophy ta, — embraces the re- 

 maining vegetable population, which may be arranged ap- 

 IDroximately in the order of development or of elaboration, 

 thus : mosses and liverworts ; ferns ; the equisetae or 

 horsetails ; the lycopodiums or club-mosses and their near 

 relations: then the flowering plants, beginning with the 

 coniferae,— the pines, firs, cypresses, yews, and the cycas, 

 which have naked seeds, usually in cones, — and ending with 

 the multitude of trees, shrubs and herbs having their seeds 

 enclosed in seed-vessels, and divided into those the stems of 

 which increase in size by additions throughout their thick- 

 ness, like the palms among trees, and the lilies among 

 herbs, and those which increase in size by growth on the ex- 

 terior of the wood immediately under the bark — thus 

 showing year-marks if they be perennials ; this division in- 

 cluding such trees as the oak, and such herbs as the violet. 



While differing enormously among themselves in every 

 respect except one, the leading difference which runs 

 through this classification is in the method of reproduction, 

 and the structure of the reproductive organs. In the verv 

 lowest plant-forms, multiplication seems to depend simply 

 u])on the strength of the cell membrane. The single cell 

 increases in size, and a partition is formed across it. If the 

 membrane be weak, the two cells part company, and the 

 number of that species has been doubled. If the mem- 

 brane be strong, the two cells remain attached, and the pro- 

 cess of increase in size and division may continue. The pro- 

 toplasm of the unicellular plant is frequently broken into 

 fragments, each provided with cilia or tilamentous prolon- 

 gations of the protoplasin, l)y the aid of which the}- move 

 rapidly through the water in wiiich they arc formed. Grad- 

 ually each becomes covered with a coating of cellulose, and 

 begins life as a complete plant. Much higher in the scale 

 of vegetation, the power of increase by simple sub-division 



