TIJF GRAND PERIOD OF GROIVTH. 54I 



variation of its growth, which is independent of temperature, Hght, and other forces 

 which influence growth. Since, however, with the periodical variation of these latter, 

 still other periodic fluctuations in the growth in length of such a part may make 

 their appearance in addition, I have, in order to distinguish it more exactly, 

 designated the phenomenon characterised above as the grand period of groivth. 



If we now take such a transverse zone as the above, limited by two lines 

 as before (but further distant from the growing-point), and then measure its lengths 

 after certain intervals of time, it is obvious beforehand that this transverse zone, 

 since it is older and further distant from the growing-point, must be from the 

 start already in a further advanced stage of growth. The case may occur, for 

 instance (if we have hit upon exactly the right distance from the growing-point), 

 that the first measured elongation forthwith coincides with the stage of maximum 

 growth, so that every further measurement must present decreasing elongations ; or 

 the zone marked by the transverse lines, if still further from the growing-point 

 may be found already from the beginning in a condition of decreasing growth, so that 

 the first measurement yields a small and each succeeding measurement an ever smaller 

 amount of growth. And if we have taken the marked zone still further removed 

 from the growing-point, it may happen that it has already ceased to elongate — that 

 therefore every succeeding measurement gives the same length. 



Thus if we had drawn a large number of transverse lines on a root, beginning 

 from the growing-point, or on a shoot-axis, beginning beneath the bud, in such a way 

 that the lines are at first equally distant from one another — say i mm. or so — then 

 on measuring the lengths of these portions after equal intervals of time, we should find 

 that the portions nearer the growing-point at first show an increasing rapidity of 

 growth, and that some one of these portions reveals a maximum rapidity, whereas 

 the transverse zones further distant from the growing-point exhibit in the same period 

 growths or elongations which are so much the less the more distant they lie from 

 the growing-point in each case. 



In order to illustrate this also by a definite example, the following observation 

 may be quoted. I had the primary root of a seedling of Vicia Faha subdivided into 

 transverse discs, each i mm. long, by means of lines of Indian ink, beginning from the 

 growing-point. After 24 hours (at 20-5° C), the root having grown in moist air, the 

 marked zones showed the following increments :■ — 



Number of transverse disc. Increase. 



(Upper) X o-i mm. 



IX 0-2 „ 



VlII 0-3 ., 



VII 0-5 „ 



VI 1-3 M 



V 1-6 „ 



IV 3-5 .. 



Ill 8-2 „ 



II 5-8 „ 



(Root-apex) I i-5 -. 



Total growth in length 23-0 mm. 



