542 



LECTURE XXXII. 



Here, then, that transverse disc in which the maximum growth took place was 

 situated above the second zone from the apex of the root; or, in other words, it was 



the third of the marked zones in which 

 an increment of 8-2 mm. resulted in the 

 24 hours — the original length being 

 I mm. Nearer to the apex, as well as 

 further from it, the amounts of growth 

 were smaller. We may thus say, shortly, 

 that at a distance of 2-3 mm. from the 

 growing-point of this root the growth 

 had attained its maximum rapidity, 

 whereas it was very slow immediately 

 behind the growing-point, and much 

 further distant from it (10 mm. in the 

 present example) only amounted to 

 o-i mm. In transverse zones still 

 further distant, no further growth at 

 all was to be detected. 



The same is the case also with shoot- 

 axes. Since in these, however, the 

 growth is distributed over longer 

 stretches, it is well to take longer 

 transverse zones at once from the com- 

 mencement. Thus, beginning from 

 the upper end of the first internode 

 of a seedling of Phaseolus midtiflorus, 

 a number of equidistant transverse 

 lines were drawn, marking off pieces or zones each 3-5 mm. long. After 40 hours 

 the lengths of these portions were measured, and the following growths found to have 

 occurred : — 



Number of zone. Increase. 



(Beneath the bud) I 2-0 mm. 



Fig. 346.— a seedling of Vicia Faba (Broad Bean), 

 beginnings of the observation. The plant is fastened 

 by means of a needle «, its root being in water : th( 

 region is divided by means of painted lines into transverse zones 

 (0 — 10). B the same plant after 22 hours, at 21° c. ; the lines, re- 

 moved some distance apart, show the distribution of the growth. 



o a cork 

 growing 



II 

 III 



IV 



V 



VI 



VII 



VIII 



IX 



X 



XI 



(Lower part of plant) XII 



2-5 

 4-5 

 6-5 



5-5 

 30 

 1-8 

 i-o 

 i-o 

 0-5 

 0-5 

 0-5 



Total growth in length 29-3 mm. 

 After what has been said above, it is now obvious that the transverse segment 

 No. IV, if we had observed it 40 hours previously, would have shown an increment of 



