MAEINE AZaJE OF THE * SEALAEK ' EXPEDITION. 127 



apical cellj and a mucli denser ramification. The absence of trichoblasts is no reason 

 to separate O. Prainii from the genus Oligocladus, for in the genus Fohjsiphonia we 

 find species with and without these organs. 



The main axis of the plant was attached by means of its long rhizoids to the 

 branches of Dasyopsis, and, as may be seen in fig. 31, the youngest part raises itself 

 from its support, grows vertically upwards, though its apex shows a slight curve. The 

 apical cell is rather long and cuts off the segments at its base by a transverse wall. 

 These ses-ments remain undivided for a Ions: time— I have counted eight of them under 



j^^v.^.„ ^^^^^.^ ^..v..,. S3 



the apical cell before the pericentral cells are begun to be cut oif. 



The dorsally placed branches arise irregularly with a distance of 3, 4, G, 7, 8, 0, and 

 even more segments between them; they bear branches of the second order on the side 

 turned towards the main axis. In some cases I observed near the apex of the main axis 

 long ramified branches alternating witJi short simple ones, but in later stages I could 

 detect no further difference. Perhaps the long ones bear the tetrasporangia and the 



short ones remain sterile, but this is a mere 



D 



The first segment of the 



branches issuing from the main axis has only short pericentral cells; the second 

 segment has pericentral cells of the normal size ; all the branches of the first and 

 second orders arise from the central tube. The size of the branches and of the main 

 axis differs considerably according to the place where the measurement is taken. The 

 main axis has a breadth of 120-200 ^ ; the branches 40-80^ in the lower parts, but at 

 the top only 12-20 /x ; the segments are IJ times as long as the diameter, and at the 



top as long as broad. 



At the top of the main axis all the branches are arranged on the dorsal side of the 

 filament, but at some distance from the apex their position is sometimes altered; this 

 is the result of a slight twisting of the cells of the main axis. 



2. OLIGOCLADrS PUSILLUS, U. Sp 



ThaUo filiformi, repente ; ramis erectis, endogenis, simplicibus, normalitcr dorsaliter 

 exeuntibus. T'ilis constantibus ex uno ordine cellularum centrali et quattuor ordinibus 

 cellularum pericentralibus. Trichoblastis numerosis, filorum apices cingcntibus. 

 Mlis latis 40-100 u. Or^anis fructificationis ignotis. Ehizoidis unicellularibus. 



Coetivy, reef, on Dasyopsis aperta ; in alcohol. 



Oligocladus pusillus, on account of the numerous trichoblasts that surround the 

 slightly curved top, stands nearer to 0. ISoldinyhii than 0. Fraimi. It is a smaller 

 plant, though its filaments are broader. Its creeping filaments give off side-branches 

 on the dorsal side at a distance of 5, 7, 12, 20 segments and even more. These 

 ascending side-branches remain simple ; when, however, they develop mto creeping 

 filaments, as occasionally happens, . they likewise give off branches on their 

 side. The creeping branches have a diameter of 100 ,», the side-branches a little less, 

 and at the top of both the diameter sinks to 40 f.. The segments have a height of 

 80-100 fx, but this sinks at the top to 20 [i and even less. 



Organs of fructification have not been observed. 



dorsal 



