CHAPTER IV. 



RICCIA AND RIELLA. 



The germ-plant of Biccia glauca is a simple, short, 

 ribbon-shaped, or three- sided shoot, consisting of homo- 

 geneous cellular tissue (PL XIII, fig. 1).* The arrange- 

 ment of the cells of the germ-plant in the direction of the 

 surface corresponds exactly with that in Pellia epiphylla. 

 Individual cells of the side edges are transformed into 

 elongated papillae which are bent forwards ; a few cells 

 of the under surface grow out into long, radicular hairs. 

 At an early period there is formed in the middle of the 

 fore edge a deep, narrow indentation, produced by the fact 

 that the growth of the lateral portions of the fore edge ex- 

 ceeds that of the middle (PI. XIII, fig. 1). In this inden- 

 tation a new shoot originates. It grows rapidly in length, 

 its fore edge becoming continually wider (PL XIII, fig. 2) ; 

 the wing-shaped lateral portions of the fore edge of the germ- 

 plant are thereby stretched far apart from one another. At 

 the same time the lateral margins of the under part of the 

 new formation amalgamate with that portion of the two 

 wings of the fore edge which is directed inwards. Shortly 

 afterwards new shoots are formed in the angles of both, 

 at the spot where the amalgamation ceases. An almost 

 hemispherical mass of cellular tissue originates at the 

 bottom of the narrow cleft. The arrangement of its few 

 cells repeats in miniature that of the germ-plant (PL XIII, 

 fig. 4). On its right and left new shoots are soon produced, 

 clearly originating from the multiplication of a single 

 cell. They amalgamate with the median shoot as soon 

 as their increase in breadth causes their lateral margins to 



* I have not been able to procure, under cultivation, the first stages of 

 development of the spores of Riccia or of Autheceros; in both genera I have 

 been limited to germ-plants which I have found in their native habitats. It is 

 strange that two of the most widely spread and common plants should germi- 

 nate with so much difficulty. 



