184 THE CLASSIFICATION OF THE TILOPTERIDACE.E. 



The well-marked oogamous (?) reproduction in tlie Tilop- 

 teridacese, together with the non-motile tetra-nucleate mono- 

 spores, at any rate in H. globosa, and the polysiphonous 

 structure of the lower part of the frond, make this family 

 rather difficult to place phylogenetically. The vegetative 

 structure separates these algae very far from the Dictyo- 

 tacesB, with which nevertheless the reproductive organs 

 show certain analogies. Again, the structure of the lower 

 part of the frond shows great similarity to that of Sphace- 

 laria, but in the latter, growth is by a well-marked apical 

 cell, not trichothallic as in the Tilopteridacese. Apart from 

 the longitudinal septa, the frond is very Ectocarpus-like, 

 and as there seems to be a tendency towards oogamous 

 reproduction in some species of that genus {i.e. in the dif- 

 ferentiation of the planogametes ^), it might not be amiss to 

 place this group near the Ectocarpacese. On the whole, how- 

 ever, it seems better to place the Tilopteridacese provisionally 

 in the oogamous division of the Phseophycese, as is done in the 

 classification adopted by Prof. Vines in his student's textbook. 

 With regard to the Tilopteridacese themselves they may 

 now be classified as follows : — 

 Family, Tilopteridacese. 

 Grenera : — 



Tilopterts Kiitz. 



Haplospora (Kjellm.) limit, mutat. 

 Species : — 



Tilopteris Mertensii Kiitz. 



Haplospora globosa (Kjellm.) limit, mutat. 



( „ arctica Kjellm. ) ? 



( ,, Kingii Farlow) ? 



^ Bornet, I.e. p. 1, et seq. Sauvageau, Observations relatives d la 

 sexualite des Pheosporees [Journal de hotanique, vol. x., Nos. 22 and 23, 

 1896 ; vol. xi., Nos. 1, 2, and 4, 1897). 



