Jime C, 1S67. ] 



JOUBNAL OF HOBTICULTUBE AND COTTAGE GAEDENER. 



38S 



^VHAT CAUSES THE VARIEGATION OF 

 LEAVES ■.' 



HIS day I liave sent you a 

 common Cabbage with tlie 

 leaves white-edged : not tliat 

 I think it of any service, 

 but because there is just 

 now so much talk of the 

 means of obtaining variegation in the foliage of plants, and 

 so many opinions are given. 



Some think that our Tricolored Pelargoniums are the 

 result of chance, wliilst others affirm them to be the result 

 of careful cross-breeding. My own experience leads me 

 to form the latter idea ; but the question to me is. Does 

 the plant absorb the colouring matter from the soil in 

 which such plant is gi'own ? If so, can the colour of the 

 foliage of plants be altered at pleasure, or at the cultivator's 

 will, like the bloom of the Hydrangea '? If so, can colour- 

 ing matter be so supplied as to form any distinct-coloured 

 foliage desired ? 



Most of us know well enough how high cultivation and 

 rank luxuriant growth spoils the variegation of the foliage, 

 and induces a hue of dark olive green, and we also know 

 how difficult it is to fix variegation sometimes. 



Ill my opinion very little practical information indeed 

 has been given as to the law of Nature, if indeed it be a 

 law, wliich causes and alfects variegation. In the case of 

 this Cabbage, Was the variegation in the germ of the seed, 

 or was it in the soil '.' WoiUd it have been so variegated 

 grown in any other place or position ? Nothing has been 

 done artificially to cause it to present the appearance which 

 it does, neither is the leaf of any other plant in the whole 

 square afl'ected in any way. 



When any one can take the seed of a plant, say of a 

 Brassica. saved carefully from a pure green plant not im- 

 pregnated with any other, and can grow from seed so saved 

 according to his will variegated plants — then, and not till 

 then, shall I think we have any practical information on 

 the subject. INIany of your readers 'will, of course, difl'er 

 from me. — F. Flitiox. 



[Our correspondent is somewhat imreasonable on this 

 mysterious subject. Florists have some " practical infor- 

 mation " relative to the production of variety in the forms 

 and coloiu's of flowers, although they could not take a seed 

 and compel it to produce a variation desu'ed. Variation in 

 colour, whether in animals or plants, is one of the many 

 phenomena in Nature concernmg which there speedily 

 arises a " Why," to which we cannot assign the " Because." 

 Why colour varies in the coats of horses and of other do- 

 mesticated animals — for it is only among those domesticated 

 that such variation occurs — defies explanation ; and simi- 

 larly inexplicable is it why some Roses are red, some white, 

 So. 823.-V01. XII., Nbw Sebies. 



and some " York and Lancaster." So, also, in the case of 

 leaves always natm'ally coloured, as those of Caladium bi- 

 color. Orchis maculata, and many others, we know not why 

 in one part the colouring should diii'er from that in another 

 part. Yet that these phenomena are unexplained is no 

 more a subject for surprise than that we cannot tell why 

 eyes are sometimes blue and sometimes hazel. We do, 

 however, know some facts connected with the variegation of 

 leaves, and they are worth gathering together. 



In the first place, it is well to remember that leaves and 

 flowers are readily changed into each other — that is, a bud 

 may be made to produce either leaves or flowers. " I 

 have, ' says jMr. ICnight, " repeatedly ascertained that a 

 blossom of a Pear or Apple tree contains parts which pre- 

 viously existed as the rudiments of five leaves. I have 

 often succeeded in obtaining every gradation of monstrosity 

 of form, from five congregated leaves to the perfect blossom 

 of the Pear- tree." So that the elaborating vessels of a leaf 

 are capable of producing secretions coloui'cd otherwise than 

 green is not a matter for astonishment. 



Now, the most usual variegation in leaves is some por- 

 tion of them being white. Dr. Morren, Professor of Botany 

 at Liege, examined microscopically the wliite portions of the 

 variegated leaves of Euonymus japonicus, Syringa \ailgaris, 

 and other plants, and he uniformly found that they had 

 cells filled with air or gas in immediate contact with the 

 clilorophyll, or colourmg substance ; but the parts of the 

 leaves which were green had no such cells filled with gas 

 in contact with the chlorophyll. Unfortunately that gas 

 was not analysed, but he concluded from his examinations 

 that a corresponding whiteness of the clilorophyll accom- 

 panied that gas. We believe that that gas is oxygen, for 

 Sennebier ascertained that the discolored parts of leaves 

 are incapable of exhaling oxygen, which the green parts 

 do exhale abundanth' when exposed to light. Now, oxygen 

 gas is a great bleaching agent, and its presence in excess 

 would cause the whiteness. As an example, from a green 

 part of a leaf of the Cabbage sent to us by Mr. Flitton, we 

 removed the cuticle and applied a solution of cliloride of 

 calcium (bleaching powder), and the green clilorophyll 

 speedily acquired the colour of the white variegated parts ; 

 now, such bleaching was efl'ected by highly oxidising the 

 chlorophyll. 



An excess of oxygen, however, sometimes generates an 

 acid m leaves, and this acid, varying in diflerent leaves, 

 and coming in contact with diflerent substances in their 

 sap, difl'ers in the colour which it produces. M. Macaire 

 Princep made experiments upon this subject. He found 

 that leaves of deciduous trees in autumn absorb oxygen 

 when exposed to light, and form an acid, which clianges 

 the green of the chlorophyll first to yellow and then to red. 

 He also fy^uid that by soaking a red leaf in a solution of 

 potash it became again green, evidently in consequence of 

 the potash neutralising the acid in the leaf. He found 

 this the case even in the red under-surface of a Cyclamen 

 leaf. He carried Ms researches further, and concluded from 

 them that the red and yellow colours of flowers arise from 

 clilorophyll being altered, as it is altered, when leaves as- 

 sume their autumnal tints. 



.-.—J No. S75.— Vol. XXSVII., Old SEEIE6. 



