BRYOPHYTES 



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 



J „,. J ^ , , Fig. 241. — Anthoceros: longi- 



separated groups. This tendency to break t^dinal section through portions 

 the sporogenous tissue into separate 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 lirst one layer 



up tne 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 of cells, then dividing to form 



sporophyte, with its sterile and elongating two layers), and the columella; 



, . , , . \ , section from middle region show- 



axis, and its sporogenous tissue broken up i„g spore mother cells with sterile 



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



possible relation to the completely inde- '^sion showing tetrads and 



, 1 J /• ., , • 1 , 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 



