54 SEAWEEDS 



ment of the other. They contain paraphyses only, 

 which are generally of great length and protrude 

 through the ostiole. Observations are desirable on 

 the paraphyses of both fertile conceptacles and 

 cryptostomata, since it is probable that minute 

 parasitic Algae have sometimes been mistaken for 

 them. There is, moreover, a difference according to 

 descriptions in their mode of growth e.g. ; it appears 

 to be acropetal in the cryptostomata of Cystoseira 

 and basipetal in those of Turbinaria. Since similar 

 cryptostomata of varying shapes, dimensions, and 

 modes of origin occur in the Laminariacecc (e.g. 

 Saccorhiza, Adenocystis) and in other Phceophycece, such 

 as Chnoospora, Hydroclathrus, and Scytothamnus, any 

 discussion of their nature must involve the con- 

 sideration of these forms as well as the conceptacles 

 of peculiar origin in Splachnidiacece bearing non- 

 sexual sporangia. 



Thuret has made some interesting experiments on 

 hybridity among Fucacecv and other Algae such 

 experiments being much facilitated by the fact that 

 impregnation takes place outside the plant. Experi- 

 ments with different genera (Fucus, Himanthalia, 

 Ascophylliwi) were unsuccessful, but he obtained 

 a hybrid between Fucus vesiculosus $ and Fucus 

 serratus $ , although Fucus vesiculosus $ could not 

 fertilise Fucus serratus $. That natural hybrids 

 occur between these species seems highly probable 

 to those who have examined large series of specimens 

 and have observed especially the variation of F. 

 vesiculosus. It must not be forgotten, however, that 

 circumstances of environment, such as growth in 



