CELLEPOUA DICHOTOMA. 405 



of the simple regularity which cliaracterizes the southern 

 variety*. 



In its minute characters C. dichotoma is very constant. 

 The zooecia are prominent and ventricose ; and the rostrum 

 below the aperture is uniformly short and blunt. The ovi 

 cells, with their silvery punctured surfaces, are a conspicu- 

 ous feature, and are developed in great profusion ; in some 

 cases they are more or less covered by a dense white crust. 

 They unite with the elevated peristome in front; and the 

 aperture in the fertile cells is much contracted. Perhaps 

 the most remarkable characteristic of this species in its or- 

 dinary state is the great development of the avicularian 

 appendages, and the variety of form which they exhibit. 

 Some are circular, of minute size, and placed on the summit 

 of a small rising on the cell-wall, which must be regarded 

 as representing the avicularian cell. These are present in 

 very great numbers, sometimes as many as three occurring 

 on a single zooecium. The prseoral avicularium has a sub- 

 triangular mandible; the rostrum on which it is placed 

 is clearly the equivalent of the rising which bears the 

 smaller form. The spatulate avicularia are often plenti- 

 fully developed, but in some specimens occur more rarely. 

 They are immersed and rather irregularly distributed; 

 but one is frequently present beside the ovicell. 



It can hardly, I think, be considered doubtful that the 

 C. attenuata of Alder is a mere variety of the present spe- 

 cies. The differences in habit are of the very smallest im- 

 portance, and are not so great as those which exist be- 

 tween the stout and slender varieties of C. dichotoma, 

 which I have just described. Mr. Alder himself mentions 

 a variety of the latter " consisting of more slender cylin- 



* "It varies a good deal in form, sometimes spreading in a palmate manner, 

 like an elk's horn, sometimes consisting of more slender cylindrical brandies 

 of nearly equal thickness thruugliout. The typical form, however, is a little 

 ventricose in the centre and not much branched." — Aluek. 



