C. A, iJAtlBEfe 107 



In our former studies^ we used this character to distinguish early and late 

 canes, in that the early canes had short basal joints, while the later ones had 

 longer ones, and we see that this method of distinguishing them was amply 

 justified. 



Besides the diflterence in length, there is also one in the thickness of the 

 branches of different orders. The ha are usually thicker than the as, and the 

 cs than the ch, and so on throughout the series, until the amount of energy 

 at the plant's disposal is exhausted. It may be postulated generally that this 

 increase in length and thickness of joint is, in the main, connected with more 

 rapid and energetic growth, and is the resultant of the action of the mass of 

 roots and leaves present and available for the conmion use of the plant. Just 

 as the leaves become successively broader and longer in the young plant, so do 

 the stems increase in size. But when we apply this strictly to the successive 

 orders of branches, we meet with another complication. A moment's thought 

 will show that the 6s in a plant are in a somewhat different position from the 

 cs and ds. All the 6s are borne on one shoot, the solitary a, but this is not the 

 case in the cs and ch, which may be borne on any of several branches. We 

 number the 6s in their order of appearance on the stem, which roughly coin- 

 cides with the time of their shooting. But in the cs we first number those 

 on 61, then those on 62, and so on (c/. PI. II). While then 61, 62, 63 are in 

 more or less strict order of development, there is no means of telling the order 

 in cl, c2, c3, etc., for it would be quite possible for the first c on 62 to arise 

 before the second on 61. And this difference in the numbering of the 6s and 

 cs places the form3r in a better position for making observations on any incre- 

 ments in size according to the date of their origin during the plant's gro^^'th. 

 For instance, by observing the measurements of successive 6s, we learn that 

 there is a tendency for an initial increase in size over the as, soon reaching a 

 maximum, and followed by a decline, when the amount of energy in the indivi- 

 dual shoot is beginning to wane. There is in fact a general tendency for the 

 6s to become thinner as we pass up a. A couple of examples, typical of a very 

 large number of plants dissected, may sufl&ce. In M.5300, IIo of the list, 

 the thickness of the four 6s are, in mm., 170, 200, 16-5, 156 ; m Kassoer III 

 the figures for the six 6s are 274, 165, 167, 140, 121, respectively. This tailing 

 off of the late 6s accounts to a certain extent for the fact which will be noted 

 later, that, in the general summation of the thickness of the branches of different 

 orders, there is less difference between the averages in os and 6s than between 

 those in the 6s and cs. There are often thin 6s at the end of the series, whereas 



1 Mem. Ill, p. 162, &c. 



