GROWTH. 



339 



Length i (apical) 



ii 2 



ii 3 



ii 4 



ii 5 



6 



Increment. 

 2*0 mm. 

 2'5 

 4'5 

 6'5 

 5*5 i> 



Length 7 



9 

 10 

 ii 



12 



Increment. 

 1*8 mm. 

 ro 

 ro 



We see that the maximum of growth took place in the 

 fourth length. In view of the small difference in the rate of 

 growth between the first and second lengths, and of the great 

 difference between the second and third lengths, we may 

 estimate the length of the punctum vegetationis in this case at 

 7 millimetres. The length of the second region is clearly 

 much greater: we may estimate it at about 21 millimetres. 

 The length of the whole growing region is therefore about 

 28 millimetres. 



It must not be supposed, however, that the growing region 

 of stems is confined to a single internode : it frequently ex- 

 tends over several internodes, the number being different in 

 different plants, as the following table drawn up by Sachs 

 will shew. 



According to Askenasy there are growing simultaneously, 

 in Galium Mollugo 8 10 internodes, in Myriophyllum 25 30, 

 in Elodea 40 50, and in Hippuris there are so many that he 

 doubts if any of them cease growing so long as the plant 

 lives. 



In roots Sachs found, as shewn in the following table, that 

 the region of most rapid growth lies much nearer to the apex 



222 



