IV 



THE JUNGERMANNIACE^ 



8i 



A) grows upright in the water, and consists of a central axis, 

 about which a membranous expansion winds Hke the thread 

 of a screw. Leitgeb ^ has carefully investigated the develop- 



FiG. 32. — Riella helicophylla (Mont.). A, A female plant enlarged ; 9 , sporogonia ; B, lateral, 

 C, ventral view of the growing point, X5oo ; x, the apical cell ; L, leaves (after Leitgeb). 



ment of the thallus in R. JielicopJiylla and R. Parisii, and found 

 that the apical growth is like that of Sphcerocarpus, and that 



^ Leitgeb (7), vol. iv. p. 74. 

 G 



