280 THE BOTANICAL MAGAZINE. [Vo i. xxiv. No. 2 sY. 



EXPLANATION OF PLATE. 



All figures are drawn with the aid of Abbe's camera, and with a 

 Leitz's achromatic tV objective and a comps. ocular 12 or an ordinary 

 ocular 4. Except where otherwise indicated all the figures refer to the 

 race ' Shinriki.' 



Figs. 1-17, Consecutive stages in the development of pollen-mother- 

 cells. 



Figs. 1-3, Consecutive stages in pre-synapsis. x 2360. 



Fig. 4, The beginning oftheconglobation of chromatin-threads.X2360. 



Fig. 5, Synapsis, x 2360. 



Fig. 6, The same cut 2\>. thick, x 2360. 



Fig. 7, Conjugation of chromatin-threads after synapsis (synizesis). 

 x 2360. 



Figs. 8—9, Spirem. Spirem-threads cut by the knife, showing many 

 sectional ends, x 2360. In Fig. 8 a nucleolus with two dwarf- 

 nucleoli and a very small one lying close to a thread. Fig. 9 shows 

 the separation of threads. 



Fig. 10, Shortening of the threads after segumentation. x 2360. 



Fig. 11, An advanced stage, showing X- or 0-shaped chromosomes, 

 x 2360. 



Fig. 12, The more advanced stage. Spindle-fibres are found around 

 the nuclear membrane, x 2360. 



Fig. 13, Somewhat similar stage in pollen-mother-cell of the race 

 ' Kishuwase.' . The nucleolus and a gemini were a little dis- 

 located by the knife in cutting, x 2360. 



Fig. 14, Tripolar spindle, x 2360. 



Fig. 15, Bipolar spindle. X 2360. 



Fig. 16, An abnormal form of chromosomes. The two gemini are 

 found very elongated, x 2360. 



Fig. 17, Nucleus in interkinesis. Longitudinal splits are visible. 

 x 2360. 



Fig. 18, Pre-synaptic stage of embryosac-mother-cell-nucleus. x 2360. 



Fig. 19, Spirem of the same. Double nature of spirem-threads can 

 be recognized at one of the ends of threads cut off by the knife, 

 x 2360. 



Fig. 20, Heterotype division of the same, x 2360. 



Figs. 21—22, Polar nuclei before the fusion. The upper one provided 

 with two nucleoli, x 1280. 



Fig. 23, Fusion accomplished. A large nucleolus is formed. X1280. 



