METHODS OF LABELLING TREES AND PLANTS. 159 



not hold paint very well or it also would be preferable to iron. 

 Copper nails should be used in securing painted labels, as iron or 

 tinned iron rusts and discolors the paint where driven in. 



Copper is chemically one of the most stable metals ; its surface 

 becomes darkened with exposure, but remains intact for an indefi- 

 nite period under ordinary conditions. It is therefore well suited for 

 labels when the names are to be incised. Names may be stamped 

 in the surface with steel dies, and to render them clearer a little 

 white lead or cement may be rubbed into the lines. Copper labels 

 could be very easily and rapidly marked by an etching process, as 

 follows : Heat a sheet of copper, rub over with etcher's wax, 

 cool, write the names with a steel point, laying bare the copper on 

 the lines of the writing, expose to nitric acid and water in equal 

 parts for a few minutes, wash, clean off the wax with turpentine, 

 and cut up the copper into suitable sized labels. Names might 

 advantageously be painted on copper with a white or light colored 

 paint. Cold rolled copper is the best to use and costs about 

 twenty-five cents a pound. 



Lead labels are often used, especiall}' in European establish- 

 ments. Numbers or names are easily stamped in their surface, 

 and they are extremel}' permanent. 



Tin is the last metal to be considered. It would make ex- 

 tremely good labels for valuable plants under the conditions of a 

 damp, warm greenhouse, where other metals are subject to extreme 

 corrosion, as it is practically imperishable. By tin is meant not 

 tinned iron, but the pure metal. It is soft, but tough, and retains 

 its surface better than any other metal that can be used for labels, 

 unless aluminum could be obtained cheap enough for that purpose. 

 Names or numbers should be stamped in its surface. Sheet tin 

 costs about seventy-five cents a pound, but as one hundred or 

 more labels according to size and thickness can be made from that 

 quantity of metal, it is not expensive. Tin would be perfectly 

 permanent in water, and therefore would make excellent labels for 

 aquatic plants. 



Slate has been used and recommended for tallies. It is first 

 painted a neutral color, and the name is then painted on the sur- 

 face so prepared. 



White porcelain labels with the letters of the name burnt in have 

 been used, but the}' are, of course, very expensive and of ques- 

 tionable value except for botanic gardens. 



