io GROWTH 



continue to grow for a long time by means of a basal intercalary vegetative 

 zone. The progress of development of the varied forms of simple and 

 compound leaves suffices to indicate the existence of extremely complex 

 growth relationships, and localized zones of active growth may appear 

 simultaneously in the lamina and also in the petiole l . 



Not only apical and intercalary vegetative zones, but also zones in 

 which only growth in length is active, may be present in trichomes, and 

 also in the filaments of algae and fungi 2 . Oedogonium affords an excellent 

 example of localized intercalary growth due to the rapid stretching of a 

 ring of cellulose deposited previously 3 . Moreover, the remarkable forms 

 assumed by unicellular Diatoms and Desmids suffice to indicate that 

 localized differences of growth are possible even in cells which retain their 

 embryonic character 4 . 



The progress of development at once shows that the different members 

 of the same plant do not all grow at the same rate, or to the same size. 

 Hence the curves representing the grand periods of growth may be low 

 and flat in one case, but steep and abruptly ascending and descending in 

 another. Similarly the curve may or may not exhibit secondary maxima 

 and minima. When stipules serve as bud-scales they develop more rapidly 

 than the other parts of the leaf, and hence possess a different growth- 

 period. In some cases a gradual preparation is made during a period of 

 slow growth for a sudden and rapid developmental activity. Thus the stalk 

 of the sporogonium of Pellia epipJiylla for a period of several months does 

 not elongate more than i or 3 mm., and may then suddenly grow as much as 

 80 mm. in length within three or four days 5 . Similarly, after the winter 

 buds have been formed on a deciduous tree, their growth entirely, or almost 

 entirely, ceases for a time, and it never recommences in those buds which 

 remain permanently dormant. 



A good example of the influence of correlation in retarding growth 

 is afforded by the sporangiopftore of Phycomyces nitcns, whose grand period 



1 Hofmeister, 1. c., p. 519 ; Goebel, 1. c., p. 212 ; Stebler, Jahrb. f. wiss. Bot., 1878, Bd. XI, 

 p. 17 ; Sonntag, ibid., 1887, Bd. xvill, p. 246 ; Uhlitzsch, Unters. iiber das Wachsthum der Blattstiele, 

 1887, and Neue Beitr. z. Wachsthum der Blattstiele, 1887 ; Rothert, 1. c., p. 28; Meissner, Bot. Ztg., 

 1897, p. 203 (Conifer leaves); Goebel, Organography, 1901, Clar. Press, p. 503; Arnoldi, Flora, 

 1900, p. 440. On floral leaves see Pfitzer, Verhandl. d. naturh.-med. Vereins zu Heidelberg, 1882. 

 N. F., Bd.il, Heft 2 ; Janse, Bot. Centralbl., 1888, Bd. xxxiv, p. 325. On tendrils, &c., cf. Chap. XII. 



2 For examples see the literature quoted in Sect. 2 ; those of Niigeli, Askenasy, and Berthold deal 

 with the growth in length of the segment-cells. On Cladophora see Klebs, Unters. a. d. Bot. Inst. 

 zu Tiibingen, 1888, Bd. II, p. 536; Brand, Bot. Centralbl., 1899, Bd. LXXIX, p. 145; Nordhausen, 

 Jahrb. f. wiss. Bot., 1900, Bd. xxxv, p. 367. On hairs see Hirsch, Funfstiick's Beitr. z. wiss. Bot., 

 1900, Bd. IV, p. i. 



3 Hofmeister, Pflanzenzelle, 1867, p. 102 ; Nageli and Schwendener, Mikroskop, 1877, 2. Aufl., 

 p. 546; Berthold, Protoplasmamechanik, 1886, p. 275. 



4 Concerning the unequal growth of cells of Spirogyra see Hofmeister, Jahreshefte d. Vereins f. 

 vaterl. Naturkunde in \Vtirtemberg, 1874, Bd. xxx, p. 219. 



' Askenasy, Bot. Ztg., 1874, p. 237. On the stamens of grasses see Sect. 5. 



