1887-88.] Colouring Matters of Leaves and Flowers. 289 



moisture may produce other results than brilliancy of colour, 

 indeed the direct opposite — paleness. This is often shown in 

 the characteristic appearance of " forced " plants, which have, 

 it may be supposed, a rapid extension from quick elaboration 

 of cell-wall, but lack substance, or such stores of reserve 

 material as we have already seen are necessary for colour- 

 production. 



(C) M. Sargot, in a paper on " The Influence of Moisture 

 on Vegetation," tabulates briefly the following results : — 

 " Plants belonging to drier regions when planted in those 

 with warm and humid atmosphere, show a certain amount 

 of blanching; their leaves are pale and thin, with elongated 

 petioles. Their fruits do not become coloured with such 

 lively tints." The tomato is instanced as colouring in such 

 regions with much less brilliancy than is common in Europe. 



(D) Certain of the influences of soils may be better 

 considered when dealing with tlie effects of increased or 

 diminished nutrition. They have little direct effect, though 

 certain colour-changes are noticeable when some plants are 

 grown in one position or another; as, for instance, is the case 

 with Raphanus JRaphanistrum, which, commonly having a 

 lilac flower, is invariably yellow when grown by the sea-shore. 

 Or again, Darwin mentions that it was pointed out by a 

 famous grower of chrysanthemums, shortly after they were 

 imported from Japan, that such plants, having a tendency to 

 vary in colour, had, until of more stable character, to be 

 carefully tested in different soils for fear of colour-change 

 resulting. 



Although it is probable that an increase In nitrates will 

 deepen the colour of the leaves, yet excess of one material 

 rather than another in the soil, unless absolutely injurious 

 to the plant, will have no effect, because of the selective 

 power of the plant, which takes in general only those sub- 

 stances which are needed. 



Where, however, the soil is particularly dry or particu- 

 larly damp, so as to affect the amount of nutrition, there we 

 have to notice various induced effects upon colouring of 

 leaves and flowers. This is seen in the leaf-colours of 

 Hanunculus Ficaria, or of Ariim maculatum, or in the flower- 

 colours of plants growing near watery places. 



(E) Climatal influences resolve themselves mainly into 



