377 



in a proleptic bunched formation of branches may be produced, in the ma- 

 jority of cases, by parasitic stimulation. As a rule, the abnormally formed 

 axes deviate structurally from normal ones^. 



Further, there belongs here retrogression to the juvenile form- in trees 

 which sprout vigorously after great injury. The so-called rosette shoots, 

 as shown for a pine in Fig. 57, result from local over-nutrition, due to the 

 fact that the trees have previously suffered very great loss of foliage 

 (usually from the attacks of caterpillars). The mobilized building sub- 

 stances, which have thus lost their province of nutrition, now stream toward 

 the dormant buds, lying between the normal clusters of needles or more 

 clearly recognizable in the form of weak whirls, and cause them to sprout. 

 Instead of clusters of needles, simple broad, sword-like needles with serrate 

 edges are then produced. In their axils, as shown in the figure, the normal 

 short shoots (clusters of needles) may 

 again be formed. 



If we consider these cases as a whole, 

 we perceive at once a feature common to 

 all. It is the excessive presence of build- 

 ing material in one part of the axis. In- 

 deed, by over-nutrition, organic sub- 

 stances, actually newly formed by the 

 leaf apparatus, are placed at the disposal 

 of a part of the axis, or an accumulation 

 of the structural material is produced pjg.. 57. Rosette shoot of a 



locally since the mobilized reserve sub- Scotch pine. 



stance does not find its normal utilization ,„ ,Heaxns of the simple sword-like needles 

 due to some injury such as attacks of r/eedle.r'mn'larKecU Uffer R^TTZEHrRlu 



caterpillers, pruning, storms, etc. If this 



excessive material reaches the existing primordial organ, it becomes 

 manifest in the increased development of the normal form, or, within the 

 compass of progressive metamorphosis, of other organic forms. If the 

 structural substances reach a vegetative point, additional organs are formed. 

 Each vegetative point is always the product of the food at its command. It 

 retains its distinctive morphology only as long as the nutritive process re- 

 mains the usual one. If the amount of structural material is increased, the 

 vegetative point forms additional primordial organs, thus changing the laws 

 of the leaf arrangement, determined by heredity. New normal, vegetative 

 points may develop in the form of buds. There are, therefore, no steadfast 

 characteristics in an organism and cultivation constantly changes the in- 

 herited structural type. 



1 Compare Zang-, Wilh., Untersuch. iiber die Entstehung- des Kiefernhexen- 

 besens. Ber. d. Kgl. Lehranstalt f. Weinbau usw. Geisenheim 1905, p. 235. Abun- 

 dant material has been furnished recently in the Naturwiss. Zeitschr. f. Land- u. 

 Forstwirtschaft. 



2 Diels, L., Jugendformen und Bliitenreife im Pflanzenreich. Berlin 1906. 

 Gebr. Borntrager. 



