270 



Siph onodadiales 



The genera are : Dasydadus Agardh, 1827 ; Batophora J. Agardh, 1854 [ = Botryophora 

 J. Agardh, 1887] ; Chlorodadus Sender, 1871. They are confined to tropical and 

 subtropical seas, except for one species of Dasydadus which occurs in the Mediterranean. 



Sub-family BORNETELLE/E. In this small group the thallus is club-shaped 



and the branch-segments of either the 

 first or second order are swollen out 

 until they come into lateral contact, 

 thus forming a continuous cortex, 

 which is encrusted with calcium car- 

 bonate. Neomeris has much the 

 appearance of an encrusted Dasyda- 

 dus, but the branching is dichotomous 

 and the terminal branch - segments 

 form a facetted cortex. Spherical 

 ' aplanosporangia ' occur in a terminal 

 position on the basal branch-segments, 

 and each produces a single 'aplano- 

 spore.' Bornetella (fig. 173) mainly 

 differs from Neomeris in its poly- 

 tomous branching, and its laterally 

 developed ' aplanosporangia ' which 

 produce a number of globular 'aplano- 

 spores ' (fig. 173 1 sp. and 3}. 



In Cymopolia the habit is different. 

 The main axial coanocyte is repeatedly 

 branched in a dichotomous manner, 

 the branch-segments being all in one 

 plane. Each branch-segment is calci- 

 fied except at the constricted joints. 

 The branches of the main axis bear 

 closely set whorls of polytomous 

 branches, the terminal segments of 

 which are hair-like and deciduous. 

 On the calcified parts of the thallus 

 the cortex consists of the swollen 

 branch-segments of the second order, 

 but only the basal branch-segments 

 persist at the uncalcified constrictions 

 of the thallus. The ' aplanosporangia ' 

 are similar to those of Neomeris and 

 are developed terminally on the basal 



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Fig. 173. 1 and 3, Bornetella oligospora 

 Solms. 1, entire plant, slightly magnified, 

 showing partly the external and partly the 

 internal structure; a, axis ; zw', branches of 

 the first order ; /, peripheral facets ; /,;, 

 calcareous zone of same; sp, 'aplanosporan- 

 gia.' 3, single 'aplanosporangium.' 2, 

 three peripheral facets of B. nitida (Harv.) 

 Mun.-Chalrn. (1 arid 3, after Solms ; %, 

 after C. Cramer; from Oltmanns. ) 



branch -segments of the calcified parts of the thallus. 



