1925] SetcJieU-Oardner : Melanophyceae 399 



(1922) of his "Morphologie unci Biologie der Algen" (p. 2 ct seq.) , 

 has come to the same conclusion. Our present conception of the 

 Ectocarpales differs from that of Oltmanns in limiting it to families 

 in "which plurilocular gametangia are present on gametophytes slightly, 

 if at all different from the sporophyte, or at least definitely macro- 

 scopic. While the families under Ectocarpales, as limited by us, pre- 

 sent a very considerable variety in the details of structural differences, 

 they have in common the possession of plurilocular gametangia giving 

 rise to nearly similar gametes (isogamy) and an identity in size and 

 structure of both gametophyte and sporophyte. The Ectocarpales are 

 closely related to the Cutleriales, but in the latter there is distinct 

 oogamy and in some species considerable differences between the two 

 generations. From the Sphacelariales, the Ectocarpales differ in the 

 absence of the conspicuous apical cell of the first mentioned and the 

 very different cell wall. The cell wall, or the older layers of it, changes 

 to black in the Sphacelariales when treated with eau de javelle, but 

 does not show this reaction in any of the Ectocarpales. The macro- 

 scopic plants of the members of the Dictyosiphonales, Desmarestiales 

 and Laminariales are known only with unilocular zoosporangia. The 

 first and last of these orders are known to have greatly reduced game- 

 tophytes. From analogy the Desmarestiales may be suspected of being 

 similar to the other two orders in this respect. 



Key to the Families 



1. Fronds prostrate, discoid, crustaceous, or pulvinate, never hollow nor carnose, 



seldom gelatinous 2 



1. Fronds erect, membranaceous or filamentous, when globular or prostrate, either 



hollow or carnose 4 



2. Fronds wholly discoid, composed of a basal disk of 1 or more layers of 



cells giving rise to erect free filaments 3 



2. Fronds crustaceous or pulvinate, consisting of a basal cushion of several 

 layers of cells with penetrating filaments below and erect, free fila- 

 ments above 5. Elachisteaceae (p. 502) 



3. Fronds small, composed of a disk of 1 or 2 layers of cells all of which give rise 



to free, erect filaments or reproductive cells 



3. Myrionemataceae (p. 453) 



3. Fronds larger (up to several cm. across), composed of a disk of more than 2 



layers of cells which give rise to erect, free filaments in sori 



4. Ralfsiaceae (p. 493) 



4. Fronds globular or flattened, carnose 6. Leathesiaceae (p. 507) 



4. Fronds elongated, erect when globular, not carnose 5 



5. Fronds membranaceous or flattened, at times hollow 6 



5. Fronds cylindrical, not membranaceous 7 



6. Sori definite, entirely projecting 8. Asperococcaceae (p. 522) 



6. Sori definite, superficial, at times partially projecting 



7. Punctariaceae (p. 513) 



6. Sori usually indefinite, superficial 10. Scytosiphonaceae (p. 530) 



