325 



VARIEGATION IN CERTAIN CULTIVATED 

 PLANTS 



M. BALASUBRAMANYAM, B.A., (Hons.), Sacred Heart College, 

 Shembaganur. 



The interesting paper by Bateson on Variegation* in certain 

 plants, led me to examine at the instance of Professor Fyson some of 

 the variegate species grown in Madras gardens, for the histological 

 details of the differently coloured patchos. 



In Pothos aurea, Linden, the patches of green and yellowish - 

 white parts are not sharply defined, partly because the loss of 

 chlorophyll as one passes from a green to a light part is gradual, 

 and partly because the green occurs in flecks in the light parts, and 

 the light in flecks in the green, so that the leaf has a softly mottled 

 appearance. On the under side the light parts are a little greener 

 than the upper as if the chlorophyll persisted longer on the under 

 side. The palisade on the lighter parts does not lose its characteristic 

 structure but only its colour. 



In some other plants the variegation takes the form of white 

 •patches, with very sharply defined edges because the chlorophyll is 

 absent throughout the section. So that the patch is pure white from 

 either side. This occurs for instance in a form of Anthurium Sp. 

 where the white spots are characterised not only by the almost 

 complete absence of chloroplasts, but also by the absence of all 

 differentiation of tissue, the cells being nearly isodiametrie. (PI. 

 II, Fig. 1.) 



In Marajita vittata variegation takes the form of narrow white 

 streaks between and parallel to the nerves which run acutely from the 

 mid-rib, only on the upper side. But the palisade tissue loses not 

 only its chlorophyll but also its characteristic form and consists of 

 rounded cells indistinguishable from the spongey parenchyma, except 

 for being colourless. The cells of the water-storage tissue of the upper 

 side are here smaller, and the whole section somewhat thinner. 

 (PI. I, Pig. 1.) 



In other species are indications of the existence of a middle 

 tissue, between the upper (palisade) and lower (spongey) tissues of the 

 mesophyll. Thus in a common garden Dracaena, round ill-defined 

 spots of slightly lighter green, about 1/16 in. diameter occur here and 

 there in the leaf. A transverse section shows the normal mesophyll 

 to comprise a layer of obviously elongated cells (the palisade), a 

 second layer of much shorter cells and five or six layers of loosely 



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