FLOWERLESS PLANTS 159 



The Liverworts. — Liverworts are mosslike plants which inhabit moist 

 localities, some living in or on the surface of water, others on rocks or 

 damp soil, and some even growing on the bark of trees. The liverworts 

 have an irregular thallus-shaped or platelike body. Rhizoids are developed 

 from the lower surface of the body. From the plant body arise upright 

 structures which bear the antheridia and archegonia. 



Their life history is nearly that of a moss. These plants may also re- 

 produce themselves asexually by means of budlike structures called gemmce, 

 The gemmae, which are formed in cup-shaped organs on the upper suiface 

 of the plant, break off and under favorable conditions may form a new- 

 plant. 



Economic Value of Mosses. — The mosses and their allies have little 

 direct economic value. Indirectly they are of much benefit to mankind. In 

 many localities they form a soft carpet, which is of great importance in 

 holding water in the soil; thus they prevent erosion. They give off not a 

 little oxygen to the atmosphere and must use considerable carbon dioxide 

 in their manufacture of starch, 



Thallophytes 



We have already defined a thallus as a plant body which has 

 no definite root, stem, or leaf. It may be platelike, ribbon- 

 shaped, threadlike, globular, or even irregular in form. 



The thallus plants may be grouped in two great divisions: 

 the Algce, water-loving thallophytes containing chlorophyll, and the 

 Fungi, thallus plants which do not contain chlorophyll. 



Fungi, Parasites, and Saprophytes. — As a direct result of the 

 lack of chlorophyll in the cells, the fungi are unable to make their 

 own food. They must obtain food from other plants or animals. 

 Some take up their abode upon living plants or animals (in which 

 case they are called parasites) ; others obtain their food from some 

 dead organic matter. The latter are called saprophytes. The above 

 facts make the group of the fungi of immense economic impor- 

 tance to man. Much of the space devoted to the fungi will be 

 given up to a consideration of the relation of parasitic and sap- 

 rophytic plants to their hosts, the living or dead organisms from 

 which they obtain their food. 



Mold. — One of the most common of all our fungi is the black mold 

 (Rhizopus nigricans) . 



Experiments to determine the Growth of Mold. — Place a piece of bread 

 in each of two wide-mouthed bottles or jars, add a little water, and ex- 



