12 COMPENDIUM OF GENERAL BOTANY. 



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

 explanation of the Lccompanying figures. One usually distinguishes 

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

 is distinguished by the readiness with which the nuclein is colored by 

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

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



FIG. 3. Successive stages of nuclear division. 1 (After Strasburger.) 



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

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

 At .Band Fa, certain arrangement and longitudinal division of chromatin-threads takes place. 

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

 in E&nd F). The two halves of the chromatin-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 formed 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-figure) disappears with the thickenings. 



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

 (E, 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- 



1 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. 



