27 



instead of complicated karyokinetic ones.l Since cytolo- 

 gic al- problems lie outside our subject, we return v/ith 

 this one reference, to the treatment of the grosser an- 

 atomical structures, 



FORM OF THE CELL 



The more highly organized a cell form may be under 

 normal conditions, the more susceptible it is to the action 

 of factors v;hich arrest development. 



In higher plants, we usually find only very simple cell 

 forms in individuals normally matured. However, "protec- 

 tive palisade cells" may be cited as examples of the oppo- 

 site. In fact in gymosperms as in angiosperms it may be 

 proved, that under abnormal life-conditions, the "protective 

 palisade" cells may be replaced by simple cell forms. The 

 needles in Pinus austriaca, developed in Bonnier' s ^ ex- 

 periments under cons^t illumination,- we will return later 

 to this series of experiments,- contained simple polyhedric 

 parenchyma elements as shown in figure 9, instead of the 

 normal protective palisade cells. Klebahn (loc, cit.) ob- 

 served the same replacement by simpler forms in leaves of 

 the anemone, after fungus infection. 



The arresting action of unfavorable life conditions upon 

 the development of the cell form maybe pointed out much 

 more emphatically in the unicellular, highly organized 

 Siphoneae, The Oodiaceae are easy to investigate and are 

 especially instructive. In normal specimens of U dotea 

 Desfontainii the leaf-like part of the thallus is""composed 

 of elongated sacs, arranged parallel and extending length- 

 wise, from which spring numerous, diversely ramified side- 

 branches With a limited period of grov/th- fhe later in turrm 

 are also extensively branched and repeatedly lobated and 

 dove-tail themselves together by means of their short ram- 

 ifications, 3 thereby giving the thallus the necessary firm 

 3S consistency. Under artificial cultivation, extending over 

 several months » the appearance is completely changed^ The 

 above mentioned parallel sacs show an abundant and undimin- 

 ished growth activity vstoieh is often indeed increased, branch- 

 ing abundantly but not forming any more "stunted shoots", 

 The firm connection betv;een the single sacs is thus lacking; 

 the thallus totally loses its characteristic form, the iso- 

 lated sacs form a loose green reticulum over the neighboring 

 ones;- the formal and functional difference between the 

 single parts of the cell is lost entirely, Coditim tomentosum 



1. Compare (Jerassimow, Me kernlosen Zellen d. Conjugaten 

 Bull. Soc» Imp. Uatur. Moscou 189g; Hathansohn, Physiol. Unter- 

 sueh, ubi amitotische Kernteilung. Pringsheim's Jahrb.1900. 

 Bd, KXX7,p. 48;Hacker,Mitosen im G-efolge amitosenahnlicher 

 Kernteilungen. Anat* Anz., 1900, Bd, XVII, p. 9. 



2, Bonnier, Infl« de la lumiere electr. continue s. la 

 forme et la struct, d. pi. Rev. gen. de 3ot.,1895, T.VII,p.B41 



3» Illustration in Kuster Anat, und Biol. d. adriat, 

 Codiaceen. Flora, 1898, Bd, LXXXY, p. 181. 



