THE FOOD OF PLANTS. 10 



transverse sections of the leaves of red-foliaged varieties of 

 Corylus or Fagus. In the cells of the palisade parenchyma and 

 of the spongy parenchyma, as in the corresponding parts of green 

 leaves, are present numerous chlorophyll grains, but the epidermal 

 cells contain red or violet-coloured cell sap. In the uninjured 

 leaves, therefore, the colour of the chlorophyll is merely masked 

 by the pigment present in the epidermis. The young leaves of 

 many plants (e.g. of oaks) are red, the leaves not becoming green 

 till later. The mesophyll of the young leaves contains numerous 

 chlorophyll bodies, as we may satisfy ourselves by studying 

 transverse sections, but in the cell sap of the cells of the assimi- 

 latory tissue, especially of the palisade parenchyma, are dissolved 

 red colouring matters. In this case the red pigment serves to 

 protect the young, more deeply situated green cells against too- 

 intense light. 



]S"eottia Nidus avis is an Orchidaceous plant which is frequently 

 met with in the humous soil of damp woods. The whole plant 

 is brown in colour ; it appears to contain no chlorophyll, a trans- 

 verse section of the stem from a place about 6 cm. below the 

 inflorescence exhibits clearly on microscopical examination the 

 epidermis, the parenchyma of the cortex and of the pith, and 

 between these a cylinder of sclerenchyma, together with the 

 vascular bundles; green chlorophyll bodies, however, are nowhere 

 to be found. If a Neottia plant is crushed and treated with 

 alcohol, it is easy to obtain a chlorophyll-green extract, which 

 fluoresces also in a manner characteristic of a chlorophyll solution. 

 In fact, Neottia, as Wiesner 2 first found, contains chlorophyll ; 

 the plant can therefore assimilate, and itself produce from in- 

 organic material a portion of the organic substance which it 

 requires, at the same time it is true obtaining another portion 

 from without. For further information we make the following 

 observation. We strip a fragment of epidermis from the ovary 

 of a Neottia flower, and examine it under high magnification. In 

 the neighbourhood of the nucleus of the cells we see roundish or 

 spindle-shaped pigment corpuscles, brown in colour, which, on 

 treating the preparation with alcohol, become green. Such 

 chromatophores we also find, though certainly not in such large 

 numbers, in the tissues of the stem, and in all cases we have to 

 do with chromatophores containing a brown pigment which, under 

 ordinary circumstances, completely masks their green colour. 



In the brown Algce belonging to the genus Fucus, the colour of 



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