( 171 ) 



the leaf' tissue made it necessary to treat the material, before being 

 embedded in paraffin, during 3 to 4 X 24 hours with a 40 pCt. 

 aqueous solution of hydrofluoric acid. After this treatment it was 

 then washed for 8 to 10 hours in streaming water, dehydrated by 

 the usual method and after treatment with chloroform embedded in 

 paraffin (melting point 62° C). 



For staining the sections 1 used at first Haematoxylin-Delafleld 

 and saffranin, according to t lie prescriptions given in Chamberlain's 

 "Methods in Plant Histology" '); but this method proved unsatisfactory 

 for differentiating the very thin-walled meristem cells. Therefore I 

 afterwards always stained with methyl green and acid fuchsin '), by 

 which very good results were obtained. 



A consequence of the treatment with hydrofluoric acid was that 

 the microtome preparations were not suitable for all observations. 

 In these cases I used hand-cut preparations, if necessary stained with 

 Haematoxylin-Delafield. 



The anatomy of the normal leaf, on which something may be 

 found in literature with Bertrand'), De Bary 4 ), Scheit 6 ) and Haber- 

 landt 6 ), is as follows. 



The epiderm of the lower and upper surface consists of relatively 

 small, cubical cells, the outer wall of which is strongly thickened 

 and provided with a strong cuticle and from which capriciously 

 shaped and canaliculate outgrowths project into the lumen of the 

 cell. (cf. Bertrand, 1. c. PI. II tig. 6, 7, 8.). In the epiderm of the 

 lower side numerous, irregularly placed stomata are found. 



Under the upper epiderm lies the palissade parenchyma, formed 

 by one continuous row of cells, slightly elongated in the direction 

 perpendicular to the leaf surface, (dimensions 13 — 21 ft by 21 — 30 ft). 

 Between the palissade cells and the lower epiderm lies the spongy 

 parenchyma, consisting of tubular cells, the diameter of which is on 

 the average 18 ft, as a rule is not more than 9 ft at a partition wall 

 between two tubes and does not reach more than 28 ft. Between 

 the cells of the spongy parenchyma remains a system of large inter- 



l i C. J. Chamberlain, Methods in Plant Histology 2nd ed. Chicago. 1905. 

 pag. 30, 38 and 54. 



-i Chamberlain. 1. c. p. 40, 44 and 68. 



s , G. E. Bertrand, Anatomie comparée des tiges et des feuilles chez les 

 Gnétacées et les Gonifères. (Annales d. Sc. nat. Botanique 5 ieme série Tome XX. 1874). 



*) A De Bary. Vergl. Anatomie der Vegetationsoigane der Phanerogamen und 

 Farne. (Handb. der Physiol. Botanik von IV, Hofmeister. Leipzig. 1877.) 



"'/ M. Scheit, Die Tracheïden-Saume der Blattbiindel der Coniferen etc. 'Jenaische 

 Zeitschr. f. Naturw. Bd. XVI. Neue Folge Bd. IX. 1883.) 



°) G. Haberlandt, Physiologische Pflanzenanatomie 2te Aufl. Leipzig. 188fi 



