544 



LECTURE XXXII. 



It is seen from this table that the growing region of a shoot-axis may embrace 

 one or several internodes. In the latter case, especially when the individual 

 internodes are sharply marked off from one another by large leaves which clasp 

 the stem, there may be present within any one of them again a transverse 

 zone situated at the base, or even beneath the node, which behaves just like 

 a growing-point, and in relation to which the increments of growth increase or 

 decrease in a similar manner. 



It will also not be superfluous to point out that measurements of this kind, 

 especially on shoot-axes, only give a clear idea when the latter have already attained 

 a certain length : for at first, when the entire shoot-axis is still short and young, 

 all the parts of it are growing in length ; only when a certain length (i. e. a certain 

 age) of the oldest portions is attained, does growth cease at certain places, and it is 

 then for the first time that we have, at a definite distance from the growing-point, 

 a region which is no longer growing, as was assumed in our last table. In addition, 

 however, the case may also occur that the growth as a whole first disappears beneath 

 the bud of a long flower-scape, while at its base it continues for some time longer, 

 proceeding from an intercalary zone of embryonic tissue. In this case then the 

 sequence of the partial growths is reversed, the shoot-axis being pushed up as it were 

 from its base. The same may take place in very different ways, even in closely 

 allied plants ; for instance, I found the usual form of distribution of growth in the 

 flower scapes of Allium atropurpureum, whereas in those of A. Porrum and A. Cepa 

 in the later stages of growth there is a basal vegetative zone with the properties 

 indicated. 



What has here been said of the roots and shoot-axes holds good generally 

 [mutatis mutandis) of all organs, so long as they possess a growing-point at their apex 

 or base, since the matter depends simply upon the passing over of the smallest 

 transverse zones from the embryonic into the definitive condition, and it is to be 

 remarked especially with respect to leaves, that the processes in question take place 

 not only in the longitudinal direction, but also in the direction of the lateral veins, 

 much as in the case of the lateral shoots of a main shoot. 



The fact that the maximum elongation in roots, as well as in shoot-axes, occurs 

 only at a certain and often considerable distance from the growing-point, together 

 with other observations, warrants the assertion that in the growing-point itself only 

 an extremely slow growth in length takes place, and that, consequently, no growth 

 in length occurs at all at the apical protuberance of the growing-point : it results on 

 careful consideration also that no growth in length can take place at the apical 

 protuberance, but, on the contrary, always occurs first beneath the apex, and reaches 

 its maximum at a greater distance from it. This remark is not superfluous, 

 since for a long time past, with incomprehensible thoughtlessness, the growing- 

 point, and particularly its apex, was held to be the place of most energetic growth 

 in length. 



If it is observed now how the apex of a shoot, as it grows upwards in the course 

 of a day, elevates itself several centimetres, or in very rapidly and actively growing 

 plants some decimetres, or moves forwards in space generally, this movement 

 must not be ascribed in any way to this so-called apical growth of the shoot: 

 on the contrary, the bud behaves in the main passively in the process, since it is 



