PH^EOPHYCE^E 65 



But the absence of cilia is not confined to this order. 

 In the Fucaccce the oospheres are motionless. In the 

 ' Tilopteridacece the homologous bodies are also motion- 

 less, while in the Ectocarpacece, Ectocarpus pusillus pro- 

 duces immobile spores in the plurilocular sporangia. 

 This physiological condition may be misleading when 

 made too much of in a morphological argument. If 

 we disregard it, and take into account the character 

 of the vegetative organs, the balance of evidence 

 points to affinity with the Phceophycece. It may be 

 objected that the trichothallic growth of Cutleria is 

 very different from that of the Dictyotacece. But it 

 may be recalled that the growth of the Aglaozonia 

 or non-sexual forms of Cutleria is not trichothallic, 

 but by marginal initials. Again, it would be unwise 

 to lay down a hard and fast rule in this matter when 

 we remember the tuft of hairs at the apical dimple 

 in young Fucus plants, for example, which may 

 indicate, as other facts do, that no great gulf 

 separates trichothallic growth from that by an apical 

 cell or group of equivalent initial cells. The 

 Didyotaccm are placed here next the Cutleriacece 

 more from contrast than implied affinity. We may 

 compare the three kinds of reproductive bodies, 

 ciliated in the one case, unciliated in the other. 

 Since such loss or absence of cilia occurs elsewhere 

 in the Phceophyccw, it appears to be more reasonable 

 to regard the Dictyotcicecc as degenerate members of 

 this group, with motionless reproductive organs 

 occurring in definite sori for the most part as in 

 Cutleriacccv, though not in conceptacular fruits as 

 in Fucacccc. 



