— 161 — 



The present material examined by me has proved to be rather 

 rich both in individuals and in species but on the whole it is rather 

 uniform. Only seldom a single species is predominant in the samples 

 such as Cocconeis binotata, Grammatophora oceanica, Mastogloia 

 inœqualis, Synedra affinis, but I have not been able to point out 

 any difference dependent on variation of the depths which range 

 from one to ten fathoms. 



The genera which characterize the material in its entirety are 

 Cocconeis and Mastogloia, which occur in numerous samples and 

 also often in a great number. 



The following species are especially predominant: Actinocycliis 

 subtilis var., Biddulphia pulchella, Climacosphenia elongata, Cocconeis 

 binotata, Cocconeis fimbriata, Euphyllodium spathulatum, Grammato- 

 phora oceanica, Mastogloia qvinqvecostata, Nav. (Dipl.) Crabro and 

 variants, Navicula Lyra, Nav. (Trachyneis) aspera and variants, 

 Rhabdonema adriaticum, Bhaphoneis amphiceros and variants, Synedra 

 lœvigata and Triceratium dubium. Freshwater forms occur quite 

 singly especially in samples from Lem Ngob (from the mangrove). 

 Plankton forms are rare and occur only as fragments. I have not 

 met with Achnanthes\baccata (compare Flora of Koh Chang, part VÏÏ, 

 p. (40 — 41) 258 — 259). Nearly all the species met with by me are 

 recorded from the Tropics and more particularly from the Malay 

 Archipelago, which previously has been well examined by eminent 

 diatomologists l ). 



The marine Diatoms of Siam have a tropical character but do 

 not occupy a peculiar position among the other East-Indian marine 

 Diatoms such as it might also be anticipated. 



l ) I have first been acquainted with the treatise of C. Mereschkowsky : 

 On Polynesian Diatoms, St. Pétersbourg 1902, when my manuscript was 

 already in press; I have therefore only been able to make use of it in 

 noting the geographical distribution of the species stated in my treatise. 



Botanisk Tidsskrift, 26. Bind. 



iJ 



