LINDSAY, ON THE PROTOPHYTA OF NEW ZEALAND. 111 
are altogether or almost unknown. The most promising 
lines of research for the local botanist—in addition to the 
mere discovery of species—are the inter-relations of the exist- 
ing to the fossil flora, and of New Zealand forms to those of 
Britain, Australia, and other parts of the world. The botanist 
who devotes himself to their examination and description 
will doubtless find New Zealand Diatoms possessed of that 
common peculiarity or attribute of all New Zealand plants— 
as well as of the lower Cryptogams wherever they occur— 
variability or inconstancy of character ; and it will try severely 
both his patience and skill to define those groups of indi- 
viduals which are known to systematists as ‘ species ”’— 
groups which appear to me in many genera at least both of 
Cryptogams and Phenogams—to have no real existence in 
nature. In all probability the large additions which must 
remain to be made to the New Zealand Diatomacee will 
contain few new species or varieties in proportion to those 
which are already known as cosmopolite, or widely diffused 
European or British forms, whether living or fossil. 
II. Desmidiacee. 
Of this large and most interesting family as it is developed 
or represented in New Zealand we as yet know nothing; 
no species having been, so far as I am aware, hitherto either 
collected or described. So little is known of this family be- 
yond Europe, where they appear to decrease in number from 
north to south, that it is impossible to predict what numbers 
or kinds—what genera or species—may be found in New Zea- 
land. But the very obscurity which surrounds our know- 
ledge of their natural history and geographical distribution 
should be a stimulus to their careful study by the local 
botanist. With a few exceptions, which occur in brackish 
water, but are not peculiar thereto, these beautiful though 
minute organisms occur in fresh water. They are supposed 
to assist in the clarification or purification of the water in 
which they occur, and to constitute the food of various 
minute aquatic animalcules. They are to be looked for, it 
would appear, if we are to be guided by the character of 
their usual habitats in Europe, in clear, still water, chiefly 
in the vicinity of peat. In limestone countries or districts 
the higher forms are rare. Several species are fossil; and, 
like the fossil Diatomacez, these fossil forms appear either 
identical with or closely allied to existing species. 
