•14 



PROCEEDINGS OF THE 



quickly and well, while evergreens containing decomposition pro- 

 ducts require protracted boiling, some changing to a brown which 

 after liO to 40 minutes boiling gradually gives way to a green ; 

 otliers remain persistently brown or even change to a black. It is 

 recommended that glass beakers should be used for treating the 

 specimens in the boiling solution. 



Drying after the greening process may be by pressure in drying 

 paper or in hot sand, the choice depending on the texture of the 

 plant and if it has greened readily ; plants which require protracted 

 boiling very frequently become discoloured in sand-drying. 



Flowers and Coloured Fruits. — Very rarely can flowers be 

 brought successfully through the boiling in copper acetate. Red 

 -and yellow flowers, in which presumably the colour is contained 

 in the plastid, are occasionally good. Sand-drying has been tried 

 with verygi'eat care, and the results obtained by some workers are 

 very pleasing, but on the whole it has been found tliat colours ob- 

 tained by drying in a cotton-wool press devised by Dr. Fothergill 

 are more brilliant and may be expected to be more stable. The 

 features of the press were described by Dr. Fothergill before the 

 Royal Horticultural Society, and an account appeared in their 

 J^ournal (JMarcli 1915, p. 40). The essential is quick drying at a 

 ifairly high temperature. Sand produces too much pressure, and 

 does not allow the moisture to dissipate so rapidly. Specimens 

 dried in the press lose, of course, some of their form, but appear 

 more substantial and are more brilliant in colour. 



Ferns. — Pteridophyta for the most part provide very suitable 

 objects for greening in copper acetate. Several of the common 

 British ferns, beech-fern, heart's-tongue, and lady-fern, require 

 long boiling, but if picked when in rapid growth a fairly good 

 colour can be obtained. Very successful results have been obtained 

 with Neplirolepis exaltata and its varieties, which were embodied in 

 an exhibition at the Natural History Museum, S. Kensington, 

 to show the amount of variation obtainable within the limits of a 

 single species. 



Mosses and Hepatics. — Experiments with frondose hepatics 

 were fairly successful, also some with foliose such as Scapania. 

 Also quite a number of mosses gave good colours, but considerable 

 difiiculty arose in the drying, as the colour ofteu deteriorated in 

 sand-drying. 



Algce require varying treatment according to their colour. 

 Fresh green algae so far as experience goes can be very success- 

 fully ti-eated with copper acetate, but for delicate algae the 

 following solution is recommended, giving good colour and better 

 fixation : Copper acetate, -2 gr. ; copper dichloride, -2 gr. dissolved 

 in 100 c.c. of boiled or distilled water. The mixture is allowed to 

 settle, when a clear solution is obtained which is used cold ; the 

 algae are immersed 12 hours or longer. The methods adopted for 

 treating red algae are staining methods, differing therefore from the 

 copper-acetate process in which the green colour is a compound 



