On the Colour of Leaves of Plants and their Autumnal Changes

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On the Colour of the Leaves of Plants and and their 
Autumnal Changes. -  By Arthur Hill Hassall M.D. Lond.
Communicated by Prof. Huxley, F.RS. Received June 21, 1092
Read Nov. 10, 1892

Chlorophyll, the name given by botanists to the green colouring matter of the leaves of plants, is not, as hitherto obtained, a simple substance, but is composed, in part at least, of constituents which are non essential to its green colour, though iron is deemed to be an indispensable ingredient.

Chlorophyll is generally regarded as an admixture of two colouring matters, a yellow and a blue; on each of these, different names have been bestowed, as Zanthophyll and Cyanophyll or Yellow Chlorophyll and Blue Chlorophyll. In the following pages the word Chlorophyll is applied exclusively to the green colouring matter of the leaves.

<s>Again <\s> Although the leaves of most plants are at one pe-riod or other of their growth  of a green colour, there are many exceptions to this and some leaves, when even in full health, are red, yellow, or even blue.

Before proceeding to describe  the results of the observations and investigations made, it will be well to point out certain preliminary difficulties presented to the action of reagents on the colouring matters as contained in the leaves themselves, arising from their epidermic covering. The epidermis not only acts as an essential protection to the contents of the cells, but pre-vents the entrance into them from without of substances which might be injurious, Thus, while gases,- as oxygen and carbon
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Arthur Hill Hassall
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On the Colour of Leaves of Plants and their Autumnal Changes, 1892. From The Royal Society, AP/69/1



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