2 55 
Algal Flora of the Tropics . 
(<?) West, ’04, p. 284 (Roy. Bot. Gards., St. Anns, Trinidad !); (f) Hieronymus, ’95, 
p. 23 (in a drain and small waterfall); (g) Martelli, ’86, p. 151 (Sciotel, Alle falde 
della Zedamba). 
These are all the records there are, and while ihey serve to show that 
Vaucheria does occur in the tropics, they point to conditions being on the 
whole unfavourable to it. An examination of the records just enumerated 
also shows that in the majority of cases the Vaucheria found was a terres- 
trial form (often growing at a higher altitude), and not aquatic. This 
seems to indicate that the water is particularly unsuitable for these forms 
in the tropics, and, bearing in mind the broad filaments generally found 
in this Alga, one inclines to the assumption that the same factor is respon- 
sible for the great scarcity of aquatic Vaucheria , as was suggested as the 
probable cause for the rarity of tropical freshwater Cladophoras and RJiizo- 
cloniums , viz. the small amount of dissolved oxygen in the water. This 
view receives some support from the fact that marine species of Vaucheria 
(i. e. forms growing in well-aerated water) are apparently not at all uncommon 
in the tropics (cf. } for instance, De Wildeman, ’00, p. 89), There are, 
however, other special features in the genus Vaucheria , which may be an 
unsuitable equipment for tropical life. The assimilatory process is decidedly 
different to that of the majority of green Algae, 1 the reserve-product being 
oil and the chloroplasts being yellowish and devoid of pyrenoids. It is 
possible that in some way or other assimilation of this type may not go 
on well amid tropical conditions (cf. below) — perhaps it is more successful 
on the land than in the water. 
Although Ceylon affords many likely localities for Botrydium I did not 
find it, and other collectors have been almost equally unsuccessful. There 
are only three records, viz. : — B. argillacenm , Wallroth (Martens, ’70, p. 298 ; 
‘in praeruptis viarum argillosis, in fossis limosis ad Ypanema, Prov. S. 
Pauli, tempore pluvio ’) ; B. granulatum (L.), Grev. (Lagerheim, ’90, p. 7 ; 
‘ En los muros de las calles exteriores de Quito ’) ; and B. granulatum (L.), 
Grev. var. aequinoctiale , W. and G. S. West (West and West, ’97 A, p. 235 ; 
‘ Loanda. Non infrequens in territor. Loandensis terris humidis argillaceo- 
arenosis, latas plagas imo urbis ipsius plateas, etc., obtegens ; mox post 
pluvias copiosas nascens, citoque tempore sicco disparens ’). Botrydium is, 
of course, a form which is fairly readily overlooked, and my main object 
is to draw attention to the few records. As far as the assimilatory process 
is concerned Botrydium is, however, in the same position as Vaucheria . 
(iii) The Confervales in the Tropics. 
In dealing with Vaucheria and Botrydium one naturally also turns one’s 
attention to the Confervales, a group to which the latter genus is now 
generally referred, whilst the inclusion of Vaucheria in the Confervales is 
1 Cf. Oltmanns, Morphologie und Biologie der Algen. Zweiter Band. Jena, 1905, p. 147. 
