288 GENERAL BOTANY 



Among the higher liverworts a more bulky plant body enables 

 these plants to live in less moist situations than the lower types 

 and to approximate more nearly in their form and structure to 

 true land plants. These higher forms closely resemble in struc- 

 ture a leaf of the higher plants and are attached, like the simpler 

 species, by means of rhizoid roots. 



The production of new plants and the wider distribution of 

 the species take place by means of nonmotile spores borne in 

 special spore cases, or sporangia, which are new structures in the 

 life history of plants thus far studied. 



RICCIOCARPUS 



Habit and habitat. Ricciocarpus (Fig. 159) is a hydrophytic 

 liverwort which floats on the surface of ponds and lakes or grows 

 on mud along the shore where the water has receded. 



The general structure of the plant body is similar to a green 

 leaf in its organization, with green chlorophyll tissue on its 

 upper exposed surface adapted for photosynthesis. The lower 

 surface is furnished with rhizoids, arid with platelike structures 

 in the form of scale leaves, which serve in part to keep the plant 

 upright .on the surface of the water. In the case of plants growing 

 on mud the rhizoids function as roots in the absorption of water 

 and soil salts. 



Gametophyte. The plant body of Ricciocarpus is the gameto- 

 phyte, which bears the reproductive organs in furrows on the 

 upper surface, back of the growing points. The reproductive 

 organs, which we have called gametangia in the algae, are here 

 more highly organized and hence have other names applied to 

 them. The male reproductive organ is called the antheridium 

 and is composed of an outer layer of cells, called wall cells, 

 which inclose and protect the inner mass of mother cells of the 

 sperms, or male gametes (Fig. 159, #). The protoplasts of these 

 mother cells differentiate to form the male gametes, and when 

 the gametes are fully formed, the walls separating the mother 

 cells are absorbed and the gametes are liberated by the rupture 

 of the antheridium at its apex. 



