LENGTH OF THE GROWING REGION. 



543 



only 4-6 mm., and if we had observed it 40 hours subsequently, an increment of only 

 5.5 mm. The segment IV simply happened to be in its stage of maximum growth 

 during the period we observed it ; or, in other words, the segment No. Ill would have 

 behaved during the next 40 hours exactly like IV, whereas the segment V had been, 

 during the preceding 40 hours, in the same stage that IV was during our obser- 

 vation. That is to say, in other words again, the whole growing region of a root, or 

 of an internode, or of any organ whatever arising from a growing-point, consists of 

 transverse zones, which, according to the age in each case (i. e. according to the 

 distance from the growing-point), are in different stages of development : each of 

 these transverse zones begins to grow slowly, then grows more and more rapidly and 

 attains a maximum growth, and then decreases and finally ceases to grow altogether. 

 Although it has been impossible hitherto to draw transverse lines in a similar 

 manner on the non-cellular utricles of such plants as Vaucheria, Mttcor and similar 

 Cceloblastae, we have nevertheless every reason to believe that even in them the state 

 of affairs is exactly similar. 



This method of observation affords us at the same time an opportunity 

 of learning how long is the piece of a root, shoot-axis or other organ which is 

 actually growing. Having drawn equidistant transverse lines, starting from the 

 growing-point of a root, or from the bud of a shoot, and finding at a certain 

 distance from the growing-point, after some time — say one or two days — that 

 certain transverse lines have not separated further from one another at all, but 

 have retained their original distance apart, this signifies that at these places no 

 more growth in length whatever is taking place, and the distance between the first line 

 which has not moved and the growing-point gives us the length of the growing 

 region of the particular organ. Even a glance at the small tables above at once 

 shows that this length is strikingly different in roots and in internodes; in the 

 primary root of the seedling of Vicia Faba growth has already ceased at a 

 distance of 10- 11 mm. from the growing-point; in the first internode of the seedling 

 shoot of Phaseolus, on the contrary, it only ceases at a distance of 12 x 3 '5 mm. 

 (i. e. about 4 cm.) behind the growing- point. The differences, however, may 

 be much greater still, according to circumstances in each case : in thin lateral 

 roots the growing portion behind the apex may be 2-4 mm. in length, while it 

 may attain a length of even 50 cm. in the long flowering scapes of some Phane- 

 rogams \ I found, for example, as follows : — 



In — Length of growing region beneath the bud. 



Fritillaria imperialis .... 7-9 cm. 



Allium For rum . . 

 Allium Cepa . . . . 

 Allium atropurpureum 

 Cephalaria procera . 

 Polygonum Sieholdi 

 Asparagus asper . . 

 Valeriana Phu . . 

 Dipsacus Fullonum . 



about 



' With respect to the distribution of growth and the lengths of the growing portions in erect 

 flowering shoots, cf. my treatise ' t^ber Wachsthum und Geoiropismus aufrechter Stengel^ in Flora, 

 1873. p. 32«- 



