67 



Aa appendix, we will udd to these the discussion 

 of hypertrophied funpus-hyphae , root-hairs 

 and other cells with apical -Growth. ' 



7, Multi miclear giant cells, which furnish the 

 transition to hyperplasias, in the detailed 

 discussion, it will he shown, that those groups 

 also are histologically well characterized for 

 which, in the present survey, only etiological 

 and ontogenetic characteristics have been cited. 



1. SILIPLEST CASES 



l^e will summarize as the "simplest cases" those in which 

 sDaorinally large cells are derived from elements of the nor- 

 mal plant body which are capable of growth and division. 



If, for example, the apical cell of an alga continues 

 Its growth, but all division is omitted, under the influence 

 of abnormal life conditions, then abnormally large cells 

 arise. We have already answered the obvious question, wheth- 

 er these are to be addded to the hypertrophies, or, perhaps 

 better, are to be designated as arrested developments, since 

 the groT/th which led to their formatjon is throoughly "nor- 

 mal" as such and the product is essentially characterized as 

 abnormal only by the omission of the process of division. 



IHhe external factors, v;hose actions bx'ing about the 

 production of abnormally large apical cells, may vary. Eny^ 

 observed that under the influence of parasites ( Chytridium 

 sphacellarum ) the apical cells of the side branches oi 

 CXadosteph^is spong iosus discontinue their division, but con- 

 tinue llieirgrovrUh and thus swell out slub-shaped at the up- 

 per end. Uo changes v/hatever are recognizable in the cell 

 contents. Similar phenomena of growth occur in Sphacelaria 

 tribuloides. '^ 



Pa dina Pavon ia furnishes a further example. Specimens 

 of the dorso-ventral algae, inverted so that they are ex- 

 posed to the light on their morpholngical under-side, uncoil 

 their spiral eage and the cells of the apical region swell 

 out into bladder-like forms .^ 



The same changes observed on apical cells and in the 

 cells of the apical region can occur also in other cells 

 capable of growth and division. Our thir.-d example should 

 also illustrate at the same time the case in v/hich, under 

 abnormal life-conditions, only the division of the protoplast 

 and the formation of the croHs-wall is omitted, while the 



!• Sntwickelung einer Chytridiee aus der Untergattung 

 Olpidlum Sitzungsber. Uaturf. Fr. Berlin, 1871, p, 93. 



2. !l?he vesicular cells of Antithainnion are not of para- 

 sitic origin but are normal forms. Compare Uestler Die Blasen- 

 aellen v. Antithamnion plumula u.s.f . Wiss. Meeresunters. , 

 U. F., 1898, Bd. III. 



3» Bitter, Anat.u. Phyfi, v* Padina Pavonia. Ber.d.D.Bot. 

 Ges., 1899, Bd, ZVII,p. 2S5,» 



