PROFESSOR DICKSON ON SOME ABNORMAL CONES OF PINUS PINASTER. 519 



EXPLANATION OF PLATES XIX., XX., XXL, XXII. 



[In Plate XIX. the figures are drawn on stone from photographs. 



In Plate XX. the figures are photo-lithographic reductions from outlines made in the following 

 manner : — Photographs of the cones were obtained (the cones having been previously painted of a 

 uniform grey colour), and on these the outlines were carefully gone over with a steel " crow-quill" and 

 Indian ink. This done, the photographs were then washed out with a solution of Cyanide of Potassium 

 (about 5 grains to the ounce of water); the outlines drawn remaining, but now, of course, on white 

 paper. These outlines, after being retouched and intensified with Lamp-black, and receiving the 

 addition of the numbers, were then photo-lithographed to the scale required, and colour added by 

 chronio-lithography. I have thought it worth while to record the above process, as it may be found to 

 be very useful in many cases where an accurate outline of a given object is required. 



The diagrams in Plates XXI. and XXII. are photo-lithographic reductions from drawings on a 

 larger scale.] 



Plate XIX. 



Figure 1. Cone II.; about natural size. The two secondary spirals by 7, which converge into one of a 

 double set by 3 at the top, are distinguished by being shaded of a lighter tint than the 

 others. The scale of convergence is obviously double. 



Figure 2. Cone III. ; somewhat magnified. Here, as in the last case, the scale of convergence near the 

 top of the cone is obviously double. 



Figure 3. Cone V.; somewhat magnified. Showing the small scales intercalated among the larger ones 

 towards the lower part of the cone. 



Plate XX. 



Figures 1 and 2 represent different aspects of Cone I.; considerably reduced. In fig. 1, two secondary 

 spirals by 9, coloured red, are seen to converge into one by 8, which is continued to the 

 top of the cone. In fig. 2, two secondary spirals, coloured blue, in a double set by 7, are 

 seen to converge into one by 13, which is continued to the top of the cone. See diagram 

 in Plate XXI. fig. 1. 



Figure 3. Cone II. ; considerably reduced. The same view as that in Plate XIX. fig. 1. Two secondary 

 spirals by 7, coloured red, are seen to converge into one of a double set by 3. The scale 

 of convergence is obviously double. See diagram in Plate XXI. fig. 2. 



Figures 4 and 5. Different aspects of Cone III.; about naturalsize. Fig. 4 is the same view as that 

 in Plate XIX. fig. 2. Two secondary spirals, coloured blue, in a triple set by 2, converge 

 into one by 5, which is continued to the top of the cone. Of the three secondary spirals 

 by 9, coloured red, the two uppermost converge into one by 8 ; which last, and the lower- 

 most of the aforesaid three, converge in their turn into one by 7. The last scale of 

 convergence (coloured purple from the blue and red spirals happening to cross) is, like 

 that near the top of Cone II., obviously double. See diagram in Plate XXII. fig. 1 . 



Figures 6 and 7. Different aspects of Cone IV.; considerably reduced. In fig. 6, two spirals by 8, 

 coloured red, about the middle of the cone, are seen to " diverge" from a single one at 

 the base. In fig. 7, two secondary spirals by 8, coloured red, converge into one by 7; 

 while, higher up, two of the spirals by 7, coloured blue, converge into one of a triple set 

 by 2. See diagram in Plate XXII. fig. 2. 



Figure 8. Cone, from Museum of Economic Botany, Royal Botanic Garden, Edinburgh; considerably 

 reduced (natural size 4J inches). The arrangement in the lower part of this cone is 

 somewhat confused, and has not been determined. From about the middle, however, up 

 to the top, a regular ■$% spiral (series J, §, T 3 3, ^, &c.) is exhibited. As has been pointed 

 out by MM. Bravais, this system is readily derivable by convergence from the system 1 , 

 4, 5, 9, 14, &c. 



