12 



COMPENDIUM OF GENERAL BOTANY. 



nuclear division or " karyokinesis," but will limit myself to the 

 explanation of the c-ccompanying ligures. One usually distinguishes 

 a "chromatin" and an "achromatin" nuclear figure. The former 

 is distinguished by the readiness with which the nuclei n is colored by 

 various stains, the latter is composed of the slightly staining portions 

 of the nuclear substance. In the illustrations tlie chromatic figure is 



Fig. S. — Successive stages of nuclear division.' (After Strasburger.) 



In A an irregularly wound thveail is formed from the nuclear network (spirem, Knauel). In 

 B and C are seen the " chromatin-granules " resulting from the breaking up of the chromatin. 

 At E and i^a certain arrangement and longitudinal division of cliroinafiii-threads takes place. 

 Somewhat previous to this the nchromatin nuclear figure makes its appearance (delicate lines 

 in J? and F). The two halves of the chromatiii-threads move along the fine achromatin lines in 

 opposite directions to the poles (J)and form the " spirem " (Knauel) stage of the daughter-cells 

 (M. O). Out of the spirem is f<irmed the network, nucleoli appear, also a nuclear membrane, 

 and the daughter-nuclei are complete. When a septum is to be formed a cellulose plate forms 

 between the two daughter-nuclei at the points where the thickenings occur on the nuclear 

 spindle: otherwise the nuclear spindle (achromatin-flgure) disappears with the thickenings. 



indicated by heavy dark lines, the achromatin figure by light lines 

 (^, F, J, M). Roux assumes hypothetically that the purpose of 

 karyokinesis is to transmit hereditary peculiarities by means of the 

 dividing decisive substances (chromatin threads or bands). How- 



' In connection "with indirect nuclear division should also be mentioned the 

 recently discovered and studied " centrospheres " or "directive spheres," small 

 spherical bodies, normally two in number, lying just outside of the nucleus, which 

 also undergo considerable change in position during nuclear division. — Trans, 



