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preservation of UIqx. 



ACCORDING to W. A. Setchell and W. J. V. Osterhout, the 

 selection of aqueous media for preserving algae for class pur- 

 poses is a matter requiring careful consideration. They 

 find, too, that no one medium can be used indiscriminately for all 

 kinds of material. The Cymiophycece are best prepared with a solu- 

 tion containing i per cent, each of chrome alum and formalin. 

 The gelatinous sheath and matrices are rendered firm by this 

 solution, the cell contents are kept in a very natural condition, and 

 in most cases the colours are retained in their ordinary tints. For- 

 malin solution, I to 2 per cent., preserves the cell contents very 

 well, but does not preserve the colours or the softer gelatinous 

 sheaths and matrices. Camphor water fails with many blue-greens, 

 and is not strong enough for species preserved in the mass and 

 associated with many bacteria. The Chlorophycece are very satis- 

 factorily preserved in any of these media, but chrome alum is 

 preferable in most cases, though membranaceous forms — li^e Ulva 

 lactena, etc. — are rendered very brittle, and are, therefore, better 

 placed in simple formalin solution. The Phceophycece. do well when 

 placed immediately in r per cent, chrome alum for three to six 

 hours, and then preserved in 2 per cent, formalin solution or 

 camphor water. Specimens for crushing may remain indefinitely 

 in chrome alum solution. The coarser forms of the Rhodophycea. 

 may be kept in excellent condition in any one of the three solu- 

 tions recommended, chrome alum preserving more colour than 

 formalin or camphor water. For finer study, specimens are best 

 left in a concentrated solution of picric acid in sea-water for twenty- 

 four hours, then washed in plain sea -water for twenty- four hours 

 longer, and preserved in camphorated sea-water. 



Such genera as Nemalion, Chai?ipia, Rhabdoma, Cystodoniiim, 

 etc., respond best to this treatment. Delicate species, like Grtf- 

 fithsia bornetiann, Calithamtiion baileyi, C. bot'reri, C. seirospermum, 

 etc., must be placed in 2 per cent, formalin in sea-water, with 

 plenty of fluid, so as not to be crushed, and though the colour 

 disappears, the cells keep their shape and the plants present a life- 



