240 



Siphonales 



Lorenz (1902) has given the name Halimediles to the fossil Alga he described as 

 Halimeda Fuggeri in 1897. Boiielna Hochstetteri Toula (1884), from the Upper Neocomian 

 of Servia, has a general habit similar to Halimeda,. For a full account of the genus 

 Boueina consult Steinmann ('99). 



Sub-family CoDiEyE. The plants of this small group have a spongy 

 thallus with a variable external form. Some of them are globular cushions, 

 some flat and lobed, and others are elongated cylindrical thalli which are 

 more or less dichotomously branched ; all are fixed to the substratum by 

 means of rhizoids. The thallus consists of a central medullary mass of 



Fig. 155. Codhim tomentosum (Huds.) Stackh. A, part of thallus shown only in outline, rather 

 less than nat. size (after Murray) ; B, transverse section across thallus, x 10 ; C, one of the 

 peripheral club-shaped branches of the cosnocyte, showing gametangia (g) and hairs (h), 

 x about 60 ; D, male gamete ; E, female gamete ; F, fusion of gametes ; G, zygote (very 

 highly magnified). (C G, after Oltmanns. ) 



densely interwoven filaments from which arise numerous, club-shaped, 

 'palisade' branches (the 'utricles' of Agardh) arranged perpendicularly to 

 the surface. The latter are closely packed to form a pseudoparenchymatous 

 tissue such as does not occur in the Udotege. The rhizoids are continuous 

 with the medullary filaments. 



Most of the medullary and rhizoidal filaments apparently become 

 secondarily septate by the formation of annular thickenings which gradually 

 increase until the lumen is completely occluded at those points. Thus, as 



