326 THE JOUKNAL OF INDIAN BOTANY. 



arranged cells. In the lighter coloured spots a few layers in the 

 middle of the spongey part are without chlorophyll (PI. II, Fig. 2). 

 The effect of the absence of colour in this deep seated portion is to 

 produce lighter spots with hazy, ill-defined outlines. 



A variegated form of Alocasia macrorhiza, Schott, said to have 

 arisen as a sport, affords a most interesting variability in the distri- 

 bution of the chlorophyll — deficient tissue. This is always quite 

 definite (as regards each layer of the leaf) without any merging as in 

 Pothos aurea, or haziness as in the Dracaena. Sometimes a plant 

 will give several pure white leaves which, however, soon wither, and 

 are succeeded by more normal ones, or else the plant of course even- 

 tually dies. Sometimes one whole half of a leaf is pure creamy white, 

 without any trace of chlorophyll, while the other half is mottled. 

 More usually the whole leaf is mottled as shown in Plate III. The 

 mottling is in various degrees of lightness, and different on the two 

 sides (compare the upper and under sides of the leaf in the plate). 



Sections through different patches show that three regions can 

 be recognised in the mesophyll, an upper (the palisade) a middle and 

 a lower (the spongey-parenchyma). Writing the colours of these 

 three regions in order from the top so that W.G.W. indicates white 

 palisade, green core' and white spongey-parenchma, We find the 

 following combinations to occur : — 



G. G. G. G. G. W. 



W. G. G. G. W. W. 



W. G. W. W. W. W. 



W. W. G. 



It will be seen that only one of the eight possible combinations 

 is absent, viz., G.W.G., or white core and fully-green cortex. 



Though the spongey-parenchyma is thicker than the core, the 

 chlorophyll, is less dense, and in a leaf held up against the light, 

 patches of W.G.W, appear to be nearly of the same tint as those of 

 W.W.G. Again when viewed by reflected light only, patches of G.G.W. 

 appear the same as those of G.W.W., because of the much greater 

 intensity of the green in the palisade tissue than in the middle region, 

 but by transmitted light they are distinguished at once except in 

 the Dracaena referred to above, so far I have not found G.W.G., 

 which would be r ever son, in Bateson's sense of W.G.W. 



A variegated Eranthemum Sp. shows the third middle layer even 

 more clearly because the cells are coloured distinctly blue. This 

 causes the leaf to have a dark bluey green colour except round the 

 margin and in patches where the normal green or a lighter colour 

 occurs. Where a vascular bundle traverses the mesophyll the blue 



