1873.] Comparative Vegetable Chromatology. 479 



differing entirely from those given above. Some of the particular 

 colouring-matters occur in very different natural orders ; whereas I have 

 found others only in one particular order, or even only in a single species 

 of plant. Much remains to be learned in connexion with this branch of 

 the subject ; but many facts seem to indicate that these various substances 

 may be due to an alteration of the normal constituents of leaves, some 

 being probably formed from chlorophyll, others from the xanthophylls, 

 and perhaps some from other constituents. So far as I have been able to 

 ascertain, their development seems as if related to extra oxidization, 

 modified by light and other varying conditions not yet understood ; and 

 it will be an interesting field for inquiry to determine how far they are 

 due to simple changes in the normal constituents of leaves — in fact how 

 far the petals of flowers are modified leaves, in colour as well as in struc- 

 ture. 



Effects of Light on Flowers. 

 I have made very few experiments with the view of ascertaining the 

 effect of a different amount of light on the petals of flowers, but what I 

 have thus learned in the case of a dark variety of the common wallflower 

 ( Cheiranthus cheiri) clearly indicates that very important facts could be 

 learned in this manner. By diminishing the exposure to light, a com- 

 plete alteration was produced in the relative amount of the colouring- 

 matters. ISTo erythrophyll was developed, which was abundant in those 

 flowers exposed to the sun, and, for an equal quantity of petals, only 

 about one third the amount of xanthophyll, and yet about the same 

 quantity of chlorophyll and lichnoxanthine were formed. The result 

 was that I had produced a temporary alteration in the proportion of the 

 colouring-matters, which corresponded closely with what is the permanent 

 condition of a different natural variety or even of a different but closely 

 allied species. Judging from certain facts which have lately attracted 

 my attention, I think it extremely probable that in some cases natural 

 varieties may be imitated in a similar temporary manner by reducing 

 the constructive energy of the plants by other means. The extension of 

 such inquiries will probably throw much light on the cause of the pro- 

 duction of different coloured varieties of the flowers of the same species 

 of plant, and show that some, at all events, may be due to permanent 

 arrested or increased development of a particular kind. 



Connexion between Fungi and Lichens. 

 Such, then, being the relation between the organs of reproduction and 

 the foliage, it is to some extent possible to understand the connexion 

 between parasitic plants like fungi, which do not derive their support 

 from the constructive energy of their own fronds, and those which are 

 self-supporting and possess true fronds. In the highest classes of plants 

 the flowers are connected with the leaves more especially by means of 

 xanthophyll and yellow xanthophyll ; whereas in the case of lichens the 



