A A 



20 



This dependence on external factors, as shown in meso- 

 phyll and epidermis, in reference to the ncuTiber of cells 

 and layers, is proved also in the multicellalar hairs of 

 many plants, the tissues of the bark, and still others,- and 

 always in the sense that v\rith decreased transpiration few- 

 TErr jgellB and cell layers are formed than under normal con- 

 ditions;-! 



S. The reduction of the cell number in the products of 

 the cambium is very striking. The varying amount of the an- 

 nual increase of our trees is well knov/n, its dependence up- 

 on external factors having been proved by research. Factors 

 acting locally re involved if the growth activity of the 

 (25) cambium is retarded by strong pressure, 2, or if the increase 

 in growth continuously remains less on the windy side than 

 on the opposite one.^ *i'sxe effect of disturbances iii nutri* 

 tion or that of unfavorable climatic life conditions, is ex- 

 pressed equally in all parts. In the far north or in an 

 Alpine climate the activity of grovrth of the cambial rir|g 



is aiv/avS'i®^^ than in lower altitudes or temperate 

 au.'* j.es,5 Oger observed this arrest ement in plants kept 



1. Mitteilungen uber das Blattegewebe einiger Moose 

 (Reduktion der Lamellen bei Feuchtkultur) in Gobal, Organ- 

 ographie, p. 364. 



E, Kuster, Ueber Stammverwachsungen. Pringsheim' s . 

 Jahrb, f. vjiss, Bot. , 1899, Bd. XXXIII, p. 487. 



3, Hartig, R. Wachstumsuntersuchungen an Fichten, 

 Forstl.- Naturwissensch. Zeitschr, , 1896, Bd. V, p« 1. 

 Compare also Busgan Bau und Leben unserer Waldbaume, Jena 

 1897, p. 98, 99, and the literature quoted therein. (Schv/ein- 

 furth and others.) 



4, Hartig, loc. cit. also Zeitschr. f. Forstl- und. 

 Jagdwesen, 1871, Bd. Ill, p. 340 (Holzuntersuch. , 1901, 

 p. 5) and oth&r places, 



5. Lazniewski, Beitr. z, Biol, der Alpenflanze^^. 

 Flora, 1896, Bd. LXXXII, p. 224. ^^Kraus , Bemerkungen ub. 

 Alter- u. Wachs turns verh. ostgronlandischer Holzgev^achse. II. 

 Deutsche Uordpolf ahrt , 1874. Kihlman, Pflanzenbiol. Studien 

 aus Russisch-Lappland. Acta Soc. F. et Fl. Fennica, T. VI, 

 Nr. 3. Helsingfors 1890. In Pinus silvestris, H. Hoffman 

 observed an abnormal lobated wood-body v/hich was produced 

 by local arrestment of the formation of 3^1em. (Ueber ab- 

 normale Holzbildung. Centrabl. f. ges, Fortwesen, 1878, 

 p. 61E; Compare Just, Jahresber., 1878, Bd. VI, 2, p. 1187). 



