;oo 



MUSCINEM. 



antheridium, makes its first appearance as a simple papilla, which, in the case of the 

 first archegonium of an inflorescence of Radula, is itself the apical cell of the 

 shoot. This papilla is detached by a septum, and is divided by a second septum 

 into two cells, the lower one of which produces the pedicel, the upper one the ventral 

 portion and neck of the archegonium. The lower cell undergoes numerous transverse 

 and longitudinal divisions into several rows of cells. In the upper cell, in the case 

 of Radula, Leitgeb states that there arise three (Kny and Strasburger assert in 

 the case of Riccia and Marchantia four) somewhat oblique longitudinal walls, by 

 which three outer cells are formed; these, on their part, enclosing an inner axial 

 cell which overtops them. This latter is divided by a septum into an upper and a 

 lower cell (see Fig. 214 bis, B). The lower cell is the central cell of the arche- 

 gonium ; the upper one subsequently 

 divides cross-wise, and forms the apical 

 stigmatic cells of the neck. While the 

 three (or four) outer cells produce the 

 wall of the ventral portion and neck of 

 the archegonium by transverse and sub- 

 sequently by longitudinal divisions — the 

 whole thus increasing in height and dia- 

 meter — the central cell divides into a 

 lower and an upper cell ; the former 

 produces the oosphere by contraction 

 and rounding off of its protoplasm ; the 

 upper one lengthens within the growing 

 neck, and forms the axial row of cells, 

 the conversion of which into mucilage 

 forms at length the canal of the neck. 



(2) The Asexual Generation or Spo- 

 rogoniuni arises and is entirely formed 

 within the growing ventral portion of the archegonium, which from this time is 

 termed the Calyptra. The sporogonium does not anywhere unite in its growth 

 with the surrounding tissue of the vegetative structure of the sexual generation, 

 even when its pedicel penetrates into its tissue. 



The external form and internal structure of the sporogonium are very different 

 in the different groups. In the Anthoceroteae it is when mature an elongated two- 

 valved pod projecting from the thallus. In the Riccieae it is a thin-walled ball 

 entirely filled with spores, and, together with the calyptra, depressed in the thallus. 

 In the Marchantieae it is a shortly-stalked ball enclosing elaters as well as spores, 

 and, after it has broken through the calyptra, bursting irregularly or opening by a 

 circular fissure and detaching an operculum. In the Jungermannieae it ripens even 

 within the calyptra, but breaks through it and appears as a ball borne upon a 

 long slender stalk ; the receptacle consists, as in the Marchantieae and Riccieae, 

 when ripe, of a single layer of cells, but separates cross-wise into four lobes, to 

 which the elaters remain attached. The elaters are, as in the Marchantieae, long 

 fusiform cells, the delicate colourless outer layer of which is thickened within by 

 from one to three brown spiral bands. 



Fig. 214 bis.— First stafje of development of the archesjo- 

 nium of Andrenfa (after Kiihn) ; A terminal arrhejronium 

 arising from the apical cell of the shoot ; b b the younjjcst 

 leaves ; B after the formation of the central cell and stig- 

 matic cell; C transverse section of the young ventral 

 portion. 



