GENERAL NOTES 22I 



The following notes and tables indicate the distribution of various floras referred to. 

 It will be noticed that sometimes in the table dealing with the cold-water flora the same 

 species is indicated as being found in the oceanic flora and the meroplanktonic group of 

 the neritic flora. This has been done to express the cosmopolitan nature of the species 

 and to indicate its association with the neritic flora generally, and is not meant to indicate 

 that the species is entirely dependent upon the coast-line. 



(i) Warm- WATER FLORA 



A. Oceanic. 



Concerning the holoplanktonic flora of tropical and subtropical waters very little can 

 be said. The reason for this is that the stations established within the tropical and sub- 

 tropical Zones at which a truly oceanic flora was obtained were very poor in diatoms. 

 The few stations on the 30th W meridian which fell within these zones provided a fairly 

 constant flora. It is interesting to note that the solenoid diatoms were poorly repre- 

 sented, while the oceanic discoid forms predominated. The genera Chaetoceros and 

 Bacteriastrnm were scarce, whereas Hemidiscus and Asterolampra were very common. 

 Several neritic species were observed associated with this oceanic flora, for example, 

 Fragilaria striatula and Melosira sulcata. Planktoniella sol also was observed in con- 

 siderable numbers, but was not so numerous as around the coast of South Africa. 



B. Neritic. 



The neritic flora of the warm waters was particularly interesting, although by no 

 means complete. Concerning the holoplanktonic species in the neritic flora, those ob- 

 served off the east coast of Africa were very characteristic, several species being found 

 in no other place in the world. This African neritic flora was composed chiefly of (i) 

 relatively large centric diatoms which by reason of the strong development of the con- 

 nective zone approximated to a spherical form, (ii) a large proportion of the levigated 

 discoids, that is, forms which produce peripheral wing-like expansions and so greatly 

 increase their internal capacity, together with (iii) large but relatively weakly siliceous 

 solenoid forms. To these must be added the ubiquitous Chaetoceros spp., which in this 

 area favour the chain formation and the production of relatively large cells with short 

 hair-like bristles. Several meroplanktonic species were observed also, occurring in small 

 spirally arranged or frondose colonies. They were in no way characteristic, but species 

 common to all coasts enjoying a temperate climate. These two sections of the neritic 

 flora of the warm waters provided a greater diversity of species than any other. 



The following table gives an idea of the distribution of the warm-water diatom flora 

 observed in the phytoplankton examined. 



