BRYuHIYTES 



109 



later the sporogenous tissue becomes two layers of cells. The outer layer 

 of the amphithecium develops a capsule wall of four or more layers, the 

 outermost one being the epidermal layer, 

 consisting of elongated narrow cells and 

 containing stomata similar to those of vas- 

 cular plants. The stomata are related to 

 the fact that the wall layers beneath the epi- 

 dermis are chlorophyll tissue, giving to the 

 sporophyte the ability to manufacture food. 

 The intermediate zone adds continuously 

 new capsule regions below; therefore in a 

 longitudinal section of a capsule the whole 

 sporogenous series may be seen, from one- 

 layered sporogenous tissue below, through 

 two-layered sporogenous tissue, mother cells, 

 and tetrads, to mature spores above (fig. 

 241). The capsule dehisces by splitting into 

 two valves, which separate downwards as 

 the spores mature, leaving the spores ex- 

 posed upon the columella (fig. 239). 



In many cases some of the sporogenous 

 cells do not form spores. These sterile 

 groups of cells break up the continuous 

 mass of sporogenous cells into more or less 

 separated groups. This tendency to break 

 up the sporogenous tissue into separate 

 smaller masses by intervening sterile tissue 

 is an important fact, which will be referred 

 to later. These sterilized and somewhat 

 modified sporogenous cells are called 

 elaters, but they are different from those 

 found among Marchantiales. This green 

 sporophyte, with its sterile and elongating 

 axis, and its sporogenous tissue broken up 



into smaller masses, is Very suggestive of a cells between ; section from upper 



possible relation to the completely inde- «***» ■ howin 8 tetra ^ and 



. * sterilized sporogenous cells. 



pendent sporophyte of the ptendophytes. 



Conclusions. — Among the Anthocerotales there is a remarkable 

 association of a primitive type of gametophyte with a highly developed 



Fig. 241. — Anthoceros: longi- 

 tudinal section through portions 

 of a sporophyte, showing bulbous 

 foot embedded in the gameto- 

 phyte; above the foot is the zone 

 of actively dividing cells elongat- 

 ing the sporophyte; the base of 

 the capsule shows the peripheral 

 chlorophyll tissue, the sporoge- 

 nous tissue (at first one layer 

 of cells, then dividing to form 

 two layers), and the columella; 

 section from middle region show- 

 ing spore mother cells with sterile 



