Box.— Vol. II.] HUS— CASSIA TOMENTOSA L. 343 



diarche Anlage der Kernspindeln in Gewebezellen eine 

 Folge ihrer longitudinalen und radialen Polaritat sei." 



Polarity is in many cases probably determined by causes 

 outside the cell; for though in the first division of the 

 pollen-mother-cells and in most divisions in vegetative cells, 

 the long axis of the spindle coincides with the long axis of 

 the cytoplasmic mass, yet there are numerous cases (both 

 in reproductive and in vegetative cells) where the long axis 

 of the spindle is placed at right angles to the long axis of 

 the cell. 



Instances of these are the spindles of the daughter nuclei 

 in pollen-mother-cells, where the nuclei have probably a 

 reciprocal influence. Though the axes of the two spindles 

 are generally parallel and at right angles to the longest axis 

 of the cell, yet it sometimes occurs that the two spindles lie 

 in planes which are at right angles to each other. More 

 striking are those divisions in the cambium cells where the 

 axis of the spindle lies at right angles to the long axis of 

 the cell. 



It seems probable that we must in many cases look out- 

 side the cell for the cause of the polarity, as is especially 

 indicated by the observations of Nemec {Flora, 1899^, 

 p. 219) on cell-division in potato-tubers, where, in a cell 

 (the surrounding cells having died) the spindle formation 

 did not take place in " monaxial " fashion, but cones were 

 formed on all sides. 



The Origin of the Cones of the Multipolar 

 Spindle. 



But few cytologists have investigated closely the origin 

 of the cones of the multipolar spindle. The first to devote 

 his special attention to this subject was Belajeff (1894), ^^ 

 whose paper "Zur Kenntniss der Karyokinese bei den 

 Pflanzen " were published the results yielded by his obser- 

 vations on the division of the pollen-mother-cells of various 

 species of Larix, Since then, in addition to Strasburger's 

 observations, the spore-mother-cells of Equisetu7n (Oster- 

 hout, 1897), and the pollen-mother-cells of CobcBa (Lawson, 



