ANTHOCEROTALES 



269 



later, in the well-known way, into elaters and spore-mother-cells, showing 

 thus a partial sterilisation (Fig. 131 A). Subsequently the intercalary 

 activity begins in the middle zone, and it adds by basipetal increments 

 respectively to the columella, the archesporial layer, and the capsular wall. 

 Such intercalary development may be held to have been of secondary 

 origin from the region corresponding to the seta of other forms, and the 



( ' -. * 



Fu,. 131. 



Xotothylas Breuielii, A. longitudinal section of the basal region of an almost mature 

 capsule, showing a short sterile columella derived from the endothecium. X 130. B, a 

 similar section, but without sterile columella. In the upper part the wall of the capsule 

 can be distinguished from the sporogenous tissue, the cells of which are differentiated into 

 spore-mother-cells (shaded), and elaters. Traced downwards, the central portion of the 

 sporogenous tissue is continuous with the endothecium, while the peripheral portion comes 

 from a layer of cells which have a common origin with the wall. X 170. C, transverse 

 section of a sporogonium like B, at the base of the fertile region ; the uniform sporogenous 

 tissue (shaded) can be seen to be composed of four central groups of cells (endothecium) 

 and a surrounding layer derived from the amphithecium. x 170. D, E, F, G, H, succes- 

 sive transverse sections of a sporogonium. in which one of the four rows of cells of the 

 endothecium is forming a sterile columella, left clear in G and H. The origin of the 

 amphithecial archesporium can be followed, x 170. (After Lang.) 



primary condition of the sporogonium will thus be a more satisfactory 

 basis for comparison with other Liverworts than its mature state. 



It might be difficult, in the absence of intermediate forms, to bring 

 this peculiar sporogonium of Anthoceros into relation at all with those of 

 other Liverworts. But within the Anthocerotales there is the genus 

 Notothylas, which bears sporogonia of small size, and of limited inter- 

 calary growth, whereas in the other genera the large sporogonia appear 



