Notes . 
274 
has a well-developed assimilating tissue system, together with abundant 
mucilage-containing cells. Now, under circumstances which favour 
assimilation, e.g. strong light, sufficient warmth, and a dry atmosphere, 
an active transpiration-current will be set up, water-vapour being 
given off in the air-spaces through the pointed inward-projecting 
cells. To make good this loss, water will pass to the receptacle 
through the rhizoids. A large part of the water is absorbed by the 
mucilage-cells, and if any of the antheridia are ripe, the walls of the 
antheridium itself, as well as those of the antherozoid mother-cells, being 
at this time largely mucilaginous, also take up water and become 
swdllen. The antheridia being closely packed together considerable 
pressure is thus set up, resulting in the expulsion of the antherozoids. 
F. CAVERS. 
Yorkshire College, Leeds. 
ALGOLOGICAL NOTES.— 
IV. REMARKS ON THE PERIODICAL DEVELOPMENT OF 
THE ALGAE IN THE ARTIFICIAL WATERS AT KEW. 
Whilst working out the algal flora of the Royal Botanic Gardens at 
Ivew for publication by the authorities, I have made several observa- 
tions on the periodicity of the flora, which I wish to remark upon 
more fully here. The flora 1 was found to be built up of a hot-house 
element, consisting for the greater part of Cyanophyceae ; of the 
Thames element, due to the universal use of river-water throughout 
the gardens ; and, lastly of the open-air terrestrial element. 
The blue-green Algae, which abound in every moist hot-house, have 
received much attention from continental algologists, with the result 
that they are fairly well known. How far some of the forms may be 
looked upon as truly exotic and as introduced together with the higher 
plants, cultivated in the houses, it is difficult to say 2 . It should be 
observed that some of these blue-green forms (e. g. Symphyosiphon 
1 The constitution of the flora will be more fully discussed in the introduction 
to the algal flora of Kew Gardens. (See The Fauna and Flora of the Roya 1 
Botanic Gardens, Kew, which is to be published in the course of this year.) 
2 A large number of the blue-green Algae, which occur in the moist heat of 
greenhouses, have also been observed in hot springs of different parts of Europe, 
notably those of Carlsbad ; this seems to show that they are now truly indigenous 
in Europe, but can only exist under the peculiar conditions (i. e. high temperature 
and moisture) found at these particular spots. 
