30 ON GROWIH ANI> EXTENSION IN THE VEGETABLE KINGDOM. 



ing-wax, only in that case it is necessary that the roots them- 

 selves be in water or in moist earth above the points. It is worthy 

 of remark that precisely at the point where the absorbing surface 

 commences, tliere also the vessels with tlieir accompanying cel- 

 lular tissue commence. 



It has been said above that the granules in the cells of the 

 root-points turned blue with iodine, and consequently consisted 

 of starch, whilst those in the other cells of the root turned brown 

 with iodine. Granules of the latter kind, from the size of starch 

 granules down to the minutest size, more or less closely crowded 

 or loosely scattered, are very common in the cells of plants. 

 They are usually white, but often coloured red, green', or yellow, 

 and not unfrequently it is to them that is due tlie colouring- 

 matter of the Huid contained in the cells. The chlorophyll, or 

 the generally diffused green colour in the vegetable kingdom, is 

 owing chiefly to this cause. These granules of the cells are 

 sometimes evidently hollow inside, and they have on that account 

 been sometimes called also cells, whicli, however, may give rise 

 to, and has given rise to, a great deal of misunderstanding. 

 "When they are collected in masses in a cell, they appear clearly 

 to be enclosed in a special coating, and they represent perfectly 

 formed globules. In the cells they take sometimes one position, 

 sometimes another along the walls. Although they may belong 

 to the general category of cells, yet they must be distinguished 

 from those cells within which they are found, and of which the 

 different parts of plants are formed. We may call them cell- 

 granules. 



Leaves also, or at least long, narrow, sheathing leaves, grow 

 in a similar manner. An experiment of this kind is represented 

 in Plate 1 of my Anatomy of Plants. On a young leaf of 

 Amaryllis (Sprekelia) formosissima I had ^marked with threads 

 ten intervals of four lines each, the lowest thread being likewise 

 four lines distant from the base of the leaf in the bulb. After 

 two months the lowest thread was 4 inches 8 lines distant from 

 the base, the first interval had only stretched to 4i lines, the 

 others remained unaltered. It was therefore the lowest part of 

 the leaf, immediately above the scales of the bulb, which had 

 grown the most, and had pushed onwards the upper portion of 

 tlie leaf, with its point, in the same manner as the root-point is 

 pushed forward by the growth of the fibre. It is at that point 

 therefore that the last additional cells must be sought for. And 

 in fact we here find (see the above quoted work, Plate 1, Fig. 4), 

 close above the bulb-trunk,* which is readily known by its 



* A root consists firstly, and essentially, of the hulb-triink, a shortened 

 stem, or corm, which is distinguished from the real stem in this, that the 



