200 LINDSAY, ON THE PROTOPIYTA OF ICELAND. 
of Southern Europe also contain fossilised Diatoms, and 
these rocks are also very largely distributed in Iceland.* It 
is unnecessary further to indicate the probable habitats of 
Diatoms in Iceland. Sufficient has been said to show that 
there are few portions of Northern Europe more likely to 
prove prolific in Diatomaceous vegetation when this shall 
have been duly studied. There cannot fail to occur in Iceland 
a proportion at least of those Diatoms, which have been found 
commonly and widely distributed throughout Europe, or in 
Northern Europe, or in the North-Sea bed ; along with others 
of a more northern type or distribution. I see no reason to 
doubt, indeed, that the Diatomacee alone yet tobe detected in 
Iceland will exceed in number the whole of its 4/ge, marine 
and freshwater, as given in my ‘ Flora’ of 1861. The re- 
sultt of my very superficial gatherings from a most limited 
area in New Zealand (110 species of freshwater forms alone, 
all new to the New Zealand Flora) ought to encourage even 
tourists to undertake the work of collection, for in New Zea- 
land, as in Iceland, I was myself but a passing traveller.t 
II. Desmidiacee. 
III. Palmellacee (Chroococcacee of Rabenhorst). 
I know of no record of either Desmidiacee or Palmellacee 
proper in Iceland, except the following solitary representative 
of the latter—Aphanocapsa Grevillei, Hass. (Coccochloris 
Grevillei, var. botryoides, Hass., of my ‘ Flora,’ p. 86) —which 
occurs throughout Germany, Holland, and England; while 
the following very short list includes all the— 
IV. Chlorospermous Alge. 
I have found on record— 
1. Nostochacee. 
1. Nostoc§ commune, Vauch. 
Occurs throughout Europe. 
* Palagonite tuff is regarded by geologists as of aqueous origin, and 
partly, at least, a mud deposit of thermal waters. Remarks on volcanic 
tuffs and various so-called “‘ infusorial earths,” in relation to their Diatoma- 
ceous contents, will be found in my paper on K6tlugja, p. 20. 
+ As it is recorded in the last number of this Journal, p. 97. 
{ It should be a further source of encouragement to tourists that a 
hasty and superficial collection of Lichens made by myself in 1860 from a 
most limited area around Reykjavik exceeded in the number of species the 
whole catalogue of the Icelandic Lichens as known up to that time; while 
it also added many species to the said catalogue. (Vide “ Contributions to 
the Lichen-Flora of Northern Europe ;” ‘Journal of Linnean Society,’ 
‘‘ Botany,” vol. ix, p. 393.) 
§ Some recent writers transfer this genus or some of its species, which 
