OF THE STIPITATE DIATOMACEiE. 
33 
a whole forest of parasitic Diatomacese will come into view. 
The worst of this drying process is, that, in the species with 
long pedicels, the connection between the head and the stalk 
is almost sure to be broken, the former separating and falling 
to the ground. The only way to avoid this is to keep the 
plants in a mixture of one part of alcohol to six parts of 
water. The same solution is recommended as a preservative 
for many species, which are united together and form a long 
chain, as for instance Odontidium, Melosira, Diatoma, and 
Tabellaria. 
In searching for these minute plants, the collector will 
often be guided by the reddish-brown tint, which colours 
the Aigse on which they are growing, and which betrays 
their presence. This is especially the case in the bright 
sunshine, when it often happens that tufts of weed float on 
the surface of the water, upheld by the gases which have 
been generated by its rays. The quantity of Diatomacese, 
which are sometimes found on the larger Aigse, is almost 
incredible. Species of the genus Cocconeis (Plate viii. figs. 
38, 39) not unfrequently clothe Confervacese (for instance, 
Cladophora glomerata) with a deep red brown colour, to 
such an extent that not a trace is to be seen of the original 
green tint of the Cladophora. The Polysiphonise and 
Ceramia are not unfrequently so completely hidden under 
masses of Synedra and Achnanthes, that in point of fact 
they become, not independent plants, but the invisible 
axis of a coating of Diatomacese ! Others, however, of 
the stipitate species occur more rarely. To secure these, 
the collector must not forget to examine closely the 
various filamentous Aigse he may chance to come across 
on his excursions, and to carry off a small piece with him. 
He must be careful, too, not to overlook those plants 
whose acquaintance he has already made earlier in the 
season ; for it often happens that a colony of Diatomacese 
will fix themselves on an Alga late in the year, of 
which not a specimen appeared when the plant was first 
examined. 
D 
