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modifications, the absorption would be lowered to a less 
extent, and such a fact, along with others, might be good 
evidence of the existence of such a mixture, produced by a 
partial natural change of one into the other. Since it is only 
within the last few weeks that I have learned the full value 
of this method, I have not yet been able to apply it in all 
cases, but some of the more important facts so far observed 
will be described below. In studying the different kinds of 
erythrophyll it is also very important to ascertain whether 
they belong to Group A, B, or C; since that alone 
may completely distinguish such as are otherwise very 
similar. 
By these various means I have been able to establish the 
existence of a number of quite distinct species of erythrophyll, 
some of which have so far been found only in particular 
groups of plants. Thus, for example, the young fronds of 
several species of tropical ferns, cultivated in hothouses, 
contain a red colour, not yet found in any other plants, which 
belongs to Group A, and, when dissolved in water or in alco- 
hol, and treated with ammonia, gives a well-marked absorp- 
tion-band between the yellow and green. A red moss, which 
in early spring produces a fine effect on the scenery of some 
parts of the Yorkshire and Derbyshire moors, contains a very 
similar colour, belonging to Group A, but completely distin- 
guished by the position of the absorption-band both of an alka- 
line and an acid solution. I have not met with this colour in 
any other plant. The leaves of some of the Pelargonia of our 
gardens contain the same red colour as that found in the 
flowers of some species, and in the purple leaves of turnips 
occurs the same substance as that in the petals of the purple 
stock and some other flowers. The purple stalks of Heracleum 
sphondylium, and probably of several other common Umbellifere, 
contain a colour which is very similar to, but does not exactly 
correspond with, that of the leaves of Tamus communis, when 
they have turned very dark in autumn. These belong to 
Group B, and so does the colour of red cabbage, which also I 
have not yet found in any other plant. The red colour of the 
leaves of the beet belongs to Group C, and is the same as that 
found in the root. The bracts about the flowers of several 
plants contain the same colouring matters as those found in 
the petals, and they often give very well-marked spectra. 
Such cases, however, produce but a very limited effect on the 
general character of foliage, and by far the most abundant 
red colouring is due to two substances of Group B, not giving 
any narrow bands, but perfectly well distinguished from one 
another by the position of the broad absorption in the green 
