23 



In his "Contributions to the Biology of the Plant 

 Celr' Klebs-L describes a singular observation on Eust- 

 rum verrucosTim . These Algae T/ere cultivated in a lO per 

 cent cane sugar solution. No Plasmolysis took place; on 

 the contrary, the cells began to divide, whereby active 

 growth was so hindered that the daughter cells divided 

 anew before they had attained their normal form; the nest 

 generation did the same. Thus, not only abnormally formed 

 cells were produced wliich varied greatly from the type of 

 the species (compare fig. 7a) , but dwarf specimens also, 

 appreciably smaller than their normal progenitors and 

 living only a Short time (compare fig. 7b). The theory 

 that some form of arrestment exists here is justifiable, 

 since the grov/th activity of the single cell ends premat- 

 urely, resulting in abnormally small individuals,^" 



In higher pl^ts, when hyiDoplasia, is shown by the pro- 

 duction of abnormally small cells, the conditions are gen- 

 (28) erally such that the period of elongation, which under 

 norm&,l conditions, would follow the last cell-division 

 either does not take place or ends prematurely. 



Of course it ^is impossible to differentiate sharply 

 between arrested developments of this kind and "normally" 

 developed tissues. Some tissues, as for example, the pal- 

 isade parench^a of many leaves and the cork and the 

 primary bark of some woody plants are exposed of cells of 

 nearly equal size. In other tissues, such as the endodermis 

 of fiscus elastica a.nd the xylem of many woody plants, the 

 volume of elements of equal value physiologically and 

 histologically, fluctuates within wide boundaries, Hartig 

 and Sanio ^ have proved for tracheal tubes, tracheids, and 

 wood fibres of various trees, that their size is not only 

 dependednt upon the season in which they are produced as 

 shov/n by a study of the annual rings, but that in various 

 annual growths, at varying heights in trees, etc, elements 

 of regularly varying size may be met v/ith. Since, in spite, of 

 all differences in normal individuals a constant average 



1. Tubinger Untersuchungen, 1888,. Bd.II,3,p. 547. 



2, It is to similar factors that also the "bastard 

 form" belonging to the genus Euastrum and described by 

 Bennet, may well ovi^e its production. Ann. of Bot, 1889, 

 Vol. IV. 171. 



3» Hartig, Th. Vollstandige Uaturgeschichte d, forstl, 

 Kulturpflanzen Beutschlands , 1851, p. 207, Sanio,. Ver- 

 gleich. Untersuchungen uber die Elementarogane des Holz- 

 korpers. Bot. Zeit. 1863, Bd. XXI, p. 128; Vergleich, 

 Untersuchungen uber die Elementarogane des Holzkorpers, 

 Bot. Zeit. 1863, Bd. XXI, p.^128; Vergleich, Untersuchun- 

 gen uber Zusammensetzung des Holzkorpers, ibid., p. 396. 

 Ueber die Grosse der Holzaellen in d. gemeinen Kiefer, 

 Pringfeheim's Jahrb. f. wissensch. Bot. 1872, Bd. VIII , p. 

 401. Anat. d. gem. Keifer, ibid. 1873, Bd. IX, p. 50, Com- 

 pare further Hammerle, Zur, Organisation von Acer Pseudo- 

 platanus. Bibl. Bot. Nr. 50, 1900, and the literature 

 quote I therein. 



