210 



PHAEOPHYCEAE 



Fucaceae: Notheia (a spurious thing). Fig. 141. 



The fihform sporophyte grows out parasitically from the base of 

 conceptacles in Hormosira and Xiphophora, though it is present 

 most commonly on the microsporangiate hosts. The thallus is soHd 

 throughout and is composed of epidermal, cortical and medullary 

 tissues, the epidermis, like that of Hormosira, possessing a cuticle. 

 The genus differs from Hormosira in that growth is secured by a 



Fig. 141. Notheia anomala. A, plant growing out from Hormosira. B, point of 

 entrance of parasite into host ( x 40). C, conceptacle with megasporangia and 

 branch shoot, ^ ( x 40). D, mature megasporangia with eight ova ( x 180). (A, 

 after Oltmanns; B-D, after Williams.) 



group of three apical cells instead of four. Branching is irregular, 

 the new branches arising in the walls of old conceptacles from basal 

 cells which were dormant during the reproductive phase. There is a 

 degenerate holdfast which is composed of colourless elongated cells 

 that penetrate the host and act as absorbing organs, although there 

 are no actual haustoria. In those portions of Hormosira that are 

 attacked by the parasite the hollow of the vesicle-like internode 

 becomes filled up by new tissue formed as a result of the stimula- 

 tion, but the parasite is apparently unable to attack Hormosira 

 unless the host is growing in areas where it is continuously sub- 



