282 Marquette, Manifestations of polarity in plant cells which usw. 



Ainongst the fungi there is a whole series in which centers have 

 been found, and in some of tliem also the central body Stands out 

 plainly in the resting as well as in the dividing cells. Of these 

 Phyllactinia 1 ) especially deserves mention for in it not only can 

 the central body be traced uninterruptedly from one cell gene- 

 ration to another but its relation to the chromatin can be clearly 

 followed. 



For a considerable period -) similar relations were described for 

 the higher plants (Phanerogams and vascular cryptogams). However, 

 the investigations concerned were largely led by conceptions which 

 had their origin in the results obtained on the zoological side; 

 they left much to be desired in regard to both perfection of 

 technique and completeness of the observations. It was not until 

 the appearance of the „Bonner Studien" 3 ) in 1897 that an 

 approximately complete account of the development of a kaiyoki- 

 netic figure in the higher plants was presented. According to 

 these observations a so-called „resting" cell shows a strictly iso- 

 tropic structure, neither within the nucleus nor in the cytoplasm 

 is there an organ or even a region which could in any way be 

 compared to a centrosonie. As nuclear division approaches, fibers 

 appear in the cytoplasm which are at first arranged radially about 

 the nucleus but later bend over tili they form a feit about the 

 nuclear membrane so that it lies as it were in a nest of fibers. 

 Then these fibers draw together more distinctly in cone shaped 

 groups, but even at this time there is no indication as to where 

 the definitive spindle poles are to lie. The bipolar spindle arises 

 from this multipolar stage, as it is called, in that the various cones 

 unite into two which are opposite each other and whose bases rest 

 against each other. After nuclear and cell division is completed 

 there apparently is no longer any trace of a polar Organization in 

 the cell, it again presents an isotropic structure. 



Our knowledge of spindle formation was further extended by 

 a large number of observers and to most widely separated species 

 of the higher plants with the result that everywhere the process 

 was found essentially the same as described by Osterhout and 

 Mottier. While some of these papers present a. carefully worked 

 out, detailed account, of spindle-formation (see for example the work 

 of Mottier on the embryosac of Lilium 4 ) and that of allen on the 



r ) Harper, R. A.: Sexual reproduction and the Organization of tlie 

 nucleus in certain mildews. (Carnegie Inst. "Washington. 1905.) 



2 ) First by (xuignard. Sur l'existence des spheres attractives dans les 

 cellules vegetales'. (Compt. Rend. T. CXII 1891. p. 539.) 



3 ) Jahrb. f. wiss. Bot. Bd. XXX. 1897. Especially Osterhout. Über Ent- 

 stehung der karyokinetischen Spindel bei Equisetum, and Mottier: Beiträge zur 

 Kenntnis der Kernteilung in den Polleuinutterzellen einiger Dikotylen und 

 Monokotylen. 



4 ) Mottier. D. M.: Über das Verhalten der Kerne bei der Entwicklung 

 des Embryosacks und die Vorgänge bei der Befruchtung. (Jahrb. f. wiss. Bot, 

 Bd. 31. 1898 .p. 125.) 



