218 Dr. F. E. Fritsch. On the Subaerial and [Jan. 2, 



sented (cf. table on p. 215) — especially the latter, which is no doubt a result 

 of the relative dryness of the atmosphere. Gelatinous adhesive forms are 

 much commoner than in the lowlands, although rarely exhibiting that 

 markedly diffluent character which is such a feature in the uplands ; the 

 species of Nostoc, for instance, occurring round about Peradeniya, are more of 

 the foliose type with a fairly consistent investment. The arches of the 

 aqueduct in the experiment station at Gangarruwa, probably owing to the 

 abundance of moisture, are exceptional, since at most points they are densely 

 overgrown by a highly gelatinous Nostoc in all hues of brown and green to 

 almost colourless. 



A few words on the subaerial Algae found on the cliffs and rocks of the 

 sea-coast may be added, based on observations made at Matara, Ambalangodda, 

 Bentotta, and Trincomalie. In all cases the substratum is probably subjected 

 to occasional spray from the sea (in stormy weather), but otherwise the 

 conditions are identical with those influencing the lowland subaerial Algae 

 generally. Cyanophyceae are the prevalent forms, and especially in the 

 higher zones their character is quite similar to that presented by the inland 

 forms above discussed. The lower parts of the cliffs and occasional rocks on 

 the sea-shore, on the other hand, tend to be colonised by a characteristic 

 assemblage of unicellular blue-green forms (species of Placoma, Radaisia, 

 Entophysalis, and Chroothece), which are more or less marine in character ; 

 their habitat is, no doubt, much more often reached by the sea-water, and 

 this factor excludes the ordinary inland algal growth to a varying extent, 

 whilst it calls forth the marine element just mentioned. The subaerial 

 algal growth on the sea-coast finds an interesting parallel in the algal 

 vegetation of fresh-water pools, which are found in the sand of the sea-shore 

 at diverse points, and will be considered in Part II of this paper ; in both 

 cases the occasional advent of sea-water brings in a modifying factor. 



(b) Algal Vegetation of the Inland Fresh-waters. 



In this section I propose to deal with the macrophytic algal vegetation 

 (both attached and floating) of the numerous pieces of inland fresh-water 

 (excluding rivers) I had the opportunity of studying. Since the essential 

 conditions influencing the character of the algal vegetation in these pieces of 

 water are much the same in all cases, I shall deal with them in detail in the 

 following discussion of the tanks, and merely point out the differences, when 

 speaking of the other pieces of fresh-water. Minor factors cause the 

 variation in the flora noticeable in the different collections of water. 



(i) Algw of the Tanks and other Large Inland Masses of Fresh-water. — 

 The tanks are pieces of fresh-water of artificial origin, and often of very 



