26o 



REPRODUCTION OF RICCIOCARPUS 



assisted by the mucilage cells or glands. The development of 

 these glandular cells on the plates, as well as on the other parts of 

 the thallus, adapt the plants to the drier terrestrial conditions to 

 which they are exposed, as was the case with the mucilaginous 

 walls of the Schizomycetes and Zygenmatales. 



(b) Sexual Reproduction of Ricciocarpus. — The gametes are 

 produced in more complex gametangia than we have as yet seen. 

 These organs are developed upon the upper surface of the thallus 



Fig. i8i. The origin and structure of the male gametangia or antheridia: 

 A, section of the thallus, showing the apical cell, x, and the early stages, 

 a, b, in the development of the antheridia. B, older antheridium with cells 

 dividing vertically. C, later stage in which the wall cells are differentiated. 

 D, mature antheridium of Marchantia, showing the numerous cells that 

 develop the male gametes and the wall cells, w. E, greatly enlarged view 

 of a male gamete after discharge from the antheridium. 



and in some species appear as lines radiating from the center of 

 the plant. The male gametangium originates from one of the 

 superficial cells of the thallus, which at first continues to divide 

 transversely after the manner of the vertical plates of chlorophyll- 

 bearing cells (Fig. i8i. A). The cells of these vertical plates 

 soon begin to divide vertically and thus form an elliptical mass 

 of cells (Fig. i8i, 5, C). As this growth goes on the outer or wall 

 cells become larger than the others and generally develop chloro- 



