94 BRITISH CHAROPHYTA. 



is first changed. With very gelatinous species waxed 

 paper should be substituted for calico. 



If the plant has submitted to a successful floating 

 out in the first instance, no further handling will be 

 necessary, but where any specimen is refractory it will 

 be found convenient to arrange and adjust it after it 

 has undergone pressure for a couple of hours or so 

 between two or three sheets of drying-paper. In this 

 damp and pliant condition the plant lends itself to easy 

 manipulation, and overlooked extraneous weeds or 

 other matter can be detected and removed. After the 

 first change of drying paper the plants should be subject 

 to very considerable pressure — ^preferably by a heavy 

 weight resting on the top rather than in a press, where 

 the pressure is liable to be unevenly distributed and 

 does not follow the shrinkage of the specimens in the 

 process of drying. 



The Charophytes naturally yield up their moisture very 

 rapidly, frequent changes of drying-paper are therefore 

 desirable. With three or four such changes the plants 

 are dry in a week or so, and are ready for the herbarium. 



It has been a common practice in preparing herbarium 

 specimens to arrange them in tufts, and there is much 

 in favour of this plan as giving a more correct idea of 

 the plants as they grow, but if adopted, care must be 

 taken that the selected plant is not too thick. On the 

 other hand, if the stems are arranged separately, the 

 comparative length of the internodes, the extent of the 

 branching, etc., are more clearly seen. In any case it 

 is advisable for some selected specimens to be arranged 

 separately. A few good fruiting whorls, and in the 

 case of Charas, portions of stem, may advantageously 

 be dried separately, to be placed in pockets for attach- 

 ment to the herbarium sheets, and thus avoid the 

 necessity of mutilating the specimens for purposes of 

 examination. 



It is also well to select a few good fruiting whorls from 

 each species collected and preserve them in a test-tube of 

 formalin solution (about 2 per cent.) for microscopic exa- 



