51 



suitable for that treatment. In either method they will usually 

 show little change of colour when exposed to light* The green is 

 often almost like that of the living plants; but in many it is more 

 blue than natural, though retaining a decided green wherever 

 chlorophyll was present in the living plant. In s<>me cases where 

 the specimens appeared brownish when removed from the boiling 

 fluid the brown colour has been replaced by green in the spirit! 

 Rarely does the colour become changed for the worse after 

 permanent mounting. 



When it is desired to preserve the green colour of dry 

 specimens that are to be exposed to light they may be boiled 

 in the solution of acetate, washed in pure water and dried, 

 either by exposure to dry air, or in dry sand, or between 



sheets of botanical paper in the usual way, the method of drying 

 being selected to avoid distortion in drying. Inflorescences of 

 grasses give good results when simply exposed to dry air. 



The colours of flowers and fruits are variously affected by this 

 treatment. Some are destroyed by it, others, e.g., the reds of rose- 

 hips and various fruits, are largely retained. Occasionally curious 

 results are obtained, as in the flowers of Salvia splendefts/m which 

 the colour disappeared from tne corolla, but remained to a 

 considerable extent in the calyx. The markings of variegated 

 plants are well retained where these are pale on a green ground ; 

 and even where due to pigments or coloured sap these colours can 

 often be recognised in the prepared specimens, even where much 

 of their intensity has been lost. 



An incidental advantage of the treatment is that the rapid 

 killing of the tissues in the boiling solution lessens greatly the 

 tendency to dismemberment by loss of leaves and even of 

 branches, so troublesome in certain groups of plants, this result 

 being more marked the shorter the time between the gathering of 

 the specimens and the boiling. It is helpful in the treatment of 

 such plants as tfedinn acre, which are apt to remain alive for 

 some time in the drying paper. It also helps to protect specimens 

 against injury from fungi, so often hurtful in fluid preparations 

 and in herbaria* 



The experiments on the numerous plants selected by me for 

 treatment were very carefully carried on by John Davidson, 

 attendant in the Botanical Department of the University, and I 

 take this occasion of expressing my appreciation of his services 

 in this investigation. 



Certain families of plants give less favourable results than one 

 usually obtains, a dark exudation appearing on the leaves of some 

 species. Probably further experiments will show means of over- 

 coming some at least of these difficulties. Of course the treatment 

 is not suitable for specimens so fragile that they would suffer 

 injury from being boiled, even where the colour is well kept. But 

 in many families the results are excellent, and in by far the most, 

 even of the less favourable, the form is scarcely affected, the 

 green parts remain clearly distinguished by their colour, and the 

 educational value of tlie specimens is by so much the greater. It 

 would be tedious to give a detailed statement of the effects of the 

 treatment on the several plants subjected to it. The method is a 



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