SUPPLEMENT 105 



short internodes, then it produced longer ones, then shorter ones once more. 

 It bore scale-leaves at the base, then foliage-leaves, and terminated in a bud, 

 enclosed in scales, destined to be the next shoot. Further, from the fact that 

 different plants of Hevea shoot at quite different times, it may be concluded 

 that external factors do not bring about the closing and opening of buds. This 

 conclusion seems all the more legitimate when we learn from SCHIMPER (1898) 

 that many Javanese trees, which also often form shoots many times in the 

 course of a year, exhibit variable behaviour on single branches. Amherstia 

 nobilis, for example, may exhibit on the same tree, at the same time, branches 

 with resting terminal buds and others which are in all stages of development. 

 What the internal causes are of periodic opening out of buds we do not know 

 for certain ; but it is quite possible that this periodicity is brought about 

 either by nutritive relationships or by correlations. Whether it might be 

 possible to induce a tree of this sort to produce leaves continuously, as is the 

 case with Albizzia or Ficus, must be left for the future to decide. Nor are we 

 able to say whether a certain periodicity is a permanent characteristic of 

 protoplasm or not. 



In this country also there are trees which during the summer lay down in 

 the bud the whole of next year's shoot with all its leaves, buds, and even flowers, 

 and these unfold in the following spring often in a remarkably short time (oak, 

 beech, &c. ; comp. JOST, 1891 ; KUSTER, 1898 ; BERTHOLD, 1904). Just as in 

 the case of Hevea, the internodes, and often the leaves also, are characterized 

 by regular differences in size, which may be present even in the bud. The 

 initiatory impulse to development in spring is in this case, doubtless, tempera- 

 ture, and hence it is possible, at least from December onwards, to induce 

 artificially unfolding of buds in most trees by raising the temperature. On the 

 other hand, it is impossible that the inhibition of shoot-formation, which occurs 

 as early as May, can be dependent on external factors. In the first place, the 

 necessary leaf primordia capable of unfolding are simply wanting ; later on, 

 in summer, they are present and able to unfold under various conditions, either 

 as a second shoot the so-called ' Lammas shoot ' which is not an infrequent 

 phenomenon in many trees such as the oak or in consequence of other circum- 

 stances which are recognizable and under experimental control. If the shoot 

 be deprived of its foliage in early summer (GoEBEL, 1880), or if it be allowed to 

 put out its leaves in darkness (Josr, 1893), thus interfering with the function 

 of the leaves, a second shoot-formation appears quite regularly. Obviously 

 correlations exist between leaves and buds of such a nature that fully functional 

 leaves keep the buds from unfolding. Possibly, in many cases, withdrawal of 

 water from the leaves (WiESNER, 1889) or of salts (BERTHOLD, 1904) inhibit 

 the buds from growing, but this kind of correlation has not been exactly estab- 

 lished. In the long run the inhibition may go on so far as to kill the apex of 

 the shoot altogether (lime-tree). The same questions have to be solved in the 

 case of these trees as in the case of the tropical ones above referred to. Their 

 periodicity, is, as we see, not unchangeable, but we cannot tell whether it is 

 possible to induce them to grow continuously. The latter view is, however, 

 quite conceivable, for in many trees, e. g. Acer or Forsythia, every transition 

 may be observed between those whose buds unfold intermittently, and those 

 whose shoots grow continuously during the whole summer. The difference 

 between our native trees with fitful unfolding of shoots, and tropical trees, lies 

 in the fact that the former as a rule shoot only once a year, viz. in spring. 

 There are certainly exceptions, one instance of which being the ' Lammas 

 shoot ' already mentioned. We have to note also that many trees (especially 

 Aesculus) form even a second shoot in autumn after they have lost their leaves 

 owing to unfavourable climatic conditions, e. g. drought. In general, how- 



