— 170 - 



Explanation of the plates. 



All figures are drawn with the aid of a camera lueida, and with a 

 Zeiss apochromatic 1,5 mm. objective, 1,30 ap. : Figs 1—15, 17, 21 and 

 29 with compens. oc. 12; Fig. 22 with compens. oc. 18; Figs 16, IS 

 —20, 23—27, 30-32 with compens. oc. 6; and Fig. 28 with objective 

 Stiassnie No. 7 and ocular No. 4. 



Plate I. 



Figs 1—7, Hieracium auricula, Pollen mothercells; 

 Fig. J, Resting stage before synapsis; 

 Figs % 4f, 5, Synapsis; 



Fig. 3, Tangential view of portion of nuclear reticulum before synapsis, showing 



the double prochromosomes; 

 Fig. 6, Multipolar spindle-formation; 

 Fig. 7, Anaphasis in the heterotypic division; 

 Fig. 8, H. venosum, Pollenmothercell, heterotypic spindle-figure ; 

 Figs 9, 10, H. auricula, Embryosac-mothercell; 

 Fig. 9, Diakinesis; 



Fig. 10, Heterotypic division; two succeeding sections; 

 Figs 11 — 15, H. excellens, Pollen mothercells; 



Figs 11 — 14, Postsynaptic stage, with longitudinal split of the chromatin threads 



and formation of the chromosomes; 

 Fig. 15 a, b, Two succeeding sections of the heterotypic spind letigure, with 



bivalent and univalent chromosomes; 

 Figs 16—24, H. excellens, Embryosac-formation; 



Fig. 16, Nucellus with postsynaptic stage in the nucleus of the embryosac- 

 mothercell; 

 Fig. 17, Heterotypic spindle-figure; 

 Fig. 18, Formation of the daughter nuclei; 



Figs 19, 20, Embryosac-formation: Taraxacum-scheme ; compare the text p. 156; 

 Fig. 21, Anaphasis in the second division; 



Fig. 22, Second division, prophasis with about 16 chromosomes; 

 Fig. 23, The embryosac-tetrad, with dwarfed nuclei; 



Fig. 24, The embryosac encroaching upon the 3 sistercells of the tetrad; 



Plate II. 



Figs 25- 32, H. excellens, Embryosac-formation: 



Figs 25—27, Embryosac-tetrad and aposporic embryosac-formation {Ap); 



Fig. 28, Typical and aposporic (Ap) embryosacs, with dividing nuclei; the 

 typical embryosac in two-nucleus-stage; the aposporic in eight-nucleus- 

 stage ; 



Fig. 29, The aposporic embryosac, in two-nucleus-stage, encroaching upon the 



full developed typical embryosac; at An an antipodal cell; 

 Fig. 30, Nearly the same stage; the typical embryosac in two-nucleus-stage; 

 Fig. 31, Two-nucleus-stage in the embryosac; 



Fig. 32, Two full developed embryosacs; the upper one probably aposporic. 



