THE HIGHER CRTPTOGAMIA. 99 



represents their arrangement. Each of the surfaces of the 

 plant has two longitudinal rows. The leaf originates from 

 the multiplication of a single cell protruding above the 

 surface of the terminal bud (PI. XIV, fig. 9). In its early- 

 stages, and in those leaves which are nearest to the fore 

 edge of the rib, the successive cell -formation corresponds 

 exactly with that of the scales of ferns. The leaves which 

 lie nearer to the membranous wing are considerably and 

 un symmetrically developed in breadth in their middle 

 region (PL XIV, fig. 8). 



The succession of the shoots in Riella, as in the other 

 Riccieae and Marchantieae, is pseudo-dichotomous. The 

 first visible ramification takes place usually in the early- 

 youth of new individuals, before the appearance of the 

 first leaves. The relation of the two side shoots to the 

 middle principal shoot, of which the development is ar- 

 rested, and the amalgamation of the latter with the former, 

 may be very easily observed in the simple cellular surface 

 (PI. XIV, figs. 4, V). 



The growth of the antheridia commences by the swelling 

 of a marginal cell of the membranous wing close to the 

 punctum vegetationis, and by the separation of the vesicular 

 protrusion from the original cell-cavity by means of a 

 transverse septum. By the exuberant growth of the cells 

 adjoining its base the rudiment of the antheridium is at 

 once surrounded by a closely-fitting sheath (PI. XIV, figs. 

 10, 11). After one or several divisions have taken place 

 in the cell of the first degree by means of transverse septa, 

 and the consequent formation of a short stalk, there occurs 

 in the hemispherical cell a series of divisions coinciding 

 with the like process in Riccia, by which there is produced 

 an oval body consisting of cubical cells, the mother-cells of 

 the spermatozoa, surrounded by a layer of large, flat cells 

 (PI. XIV, fig. 12). The growing antheridia now appear 

 deeply imbedded in the folds of the membranous wing 

 (PI. XIV, fig. 13). Antheridia and archegonia are always 

 situated on different shoots. New individuals first produce 

 antheridia. Archegonia usually appear on their shoots of 

 the third, fourth, or fifth degree. The archegonia are 

 situated in the axils of leaves, and are distinguished by a 



