OF THE STIPITATE DIATOMACE^E. 33 



a whole forest of parasitic Diatomacese will come into view. 

 Tlie 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 Algse 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 Algae, is almost 

 incredible. Species of the genus Cocconeis (Plate viii. figs. 

 38 ? 39) not unfrequently clothe Confervaceae (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 Polysiphoniae and 

 Ceramia are not unfrequently so completely hidden under 

 masses of Synedra and Adman thes, that in point of fact 

 they become, not independent plants, but the invisible 

 axis of a coating of Diatomaceae ! Others, however, of 

 the stipitate species occur more rarely. To secure these, 

 the collector must not forget to examine closely the 

 various filamentous Algae 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 Diatornaceae 

 will fix themselves on an Alga late in the year, of 

 which not a specimen appeared when the plant was first 

 examined. 



