CHLOROPHYLL -GRANULES AND THE SUN'S RAYS. 375 



be possible in a single cell of equal dimensions, but devoid of such projecting 

 trabecules. 



It is shown by very accurate investigations that the quantity of organic 

 substances formed in a cell, by the decomposition of carbonic acid, is greater the 

 greater the number of chlorophyll-granules, provided that all of them are so 

 arranged within its protoplasm that they can discharge their functions. A heap of 

 chlorophyll-granules filling the cell irregularly would be little suited to effect this 

 result. The small, green chlorophyll-granules must, on the contrary, be so arranged 

 that no one deprives another of light, and this is most easily possible, especially in 

 a many-storied plant-structure, composed of numerous cells, when the chlorophyll- 

 granules are grouped together like the stones in a mosaic, and are arranged along 

 the walls in this order. When, moreover, the light falls unhindered through certain 

 portions of wall, as through a window into the cell-cavity, all the chlorophyll- 

 granules there situated are almost equally illuminated. The larger the extent of 

 wall surface, the more chlorophyll-granules can be accommodated on it, and there- 

 fore the more abundantly can the decomposition of carbonic acid be carried on in 

 such cells. For such green multicellular tissue, whose most important function is 

 the decomposition of carbonic acid and the formation of organic substances, the 

 parietal grouping of the chlorophyll-granules, the above-mentioned infolding of the 

 inner surface of the cells, generally the increase of the inner surface of the cell- 

 walls clothed with chlorophyll, is accordingly the most advantageous arrangement 

 for the best possible utilization of the available space. 



When one speaks of the " green " of plants one thinks first of all of the foliage- 

 leaves, in which that colour is especially noticeable. The name "chlorophyll" 

 translated by " leaf -green " might lead to the idea that cells and tissues provided 

 with chlorophyll are only to be found in the leaves; but this would not at all 

 correspond to the true state of the case. Those plants which are not difierentiated 

 iuto stem and leaves, especially the many kinds of green water-plants classed under 

 the name of Algae, generally consist entirely of chlorophyll-bearing cells. In those 

 mutually-nourishing combinations named Lichens, one of the partners is without, 

 while the other is provided with, chlorophyll. 



When stem and foliage-leaves are clearly difierentiated, a portion of the tissue is 

 deprived of chlorophyll while the other portion is more or less rich in the same. 

 Chlorophyll-containing tissue is found in all the members of these stem-plants, in 

 roots, in stems, in foliage, in floral leaves, in fruits, and seeds. In tropical orchids 

 the aerial roots when dry appear white and are seemingly quite devoid of 

 chlorophyll; but when moistened their green colour is seen, because when the outer 

 porous covering is filled with water, and its cells become transparent, the colour of 

 the green tissue-layer below shines through. There are even orchids, e.g. Angr ce- 

 cum globulosum, funale, and Sallei, which, when not flowering, have no other green 

 tissue than that in the aerial roots, and in which not only the absorption of food- 

 materials, but also the working up of the absorbed nourishment, particularly the 

 decomposition of carbonic acid and the formation of organic substances, is carried 



