

Fig. 137 Phyllophora hrodiaei. A, plant ( x ^). B, carpogonial 

 branch ( x 250). Q transverse section of antheridial thallus ( x 450). 

 D, nemathecia with tetraspores ( x 125). (A, original; B-D, after 



KyHn.) 



secondary tissue has been observed near the axils of branches or at 

 the base of the frond. This is not surprising since the thaUi often 

 last for many years and the successive increments are recognizable 

 macroscopically. The plants are dioecious and the sex organs are 

 borne in nemathecial cavities in small fertile leaflets that are at- 

 tached to the main thallus. The carpogonial leaflets, which are 

 sessile or shortly stalked, arise laterally from the stipitate part of 

 the main blade. Only one cystocarp is produced from each carpo- 

 gonial nemathecium. In P. memhranifolia the carpogonial branch 

 is three-celled and after fertihzation gonimoblast filaments are 

 formed which ramify in the tissues, finally producing pedicellate or 

 sessile cystocarps. In P. hrodiaei spermatia appear to be fimction- 

 less and the carpogonium fuses directly with the auxiliary cell and 

 the carposporic generation is omitted. This must be regarded as a 

 reduction phenomenon in so far as the usual rhodophycean life 

 cycle is concerned. The tetraspores -are borne in moniliform chains 

 packed into wart-like excrescences or nemathecia which are borne 

 on the female sexual plant. In P. hrodiaei the absence of carpo- 

 spores led earUer investigators to regard the nemathecia as belong- 

 ing to a parasitic plant, which in this case was given the name of 

 Actinococcus suhcutaneus, but it has since been shown that we are 

 really deahng with a parasitic diploid generation. 



Phyllophoraceae: Ahnfeldtia (after N. O. Ahnfeldt). Figs. 138, 



139 

 The wiry and horny multiaxial thallus arises from a prostrate 



disc and is a perennial with secondary thickening. This results from 



244 



