Reproductive Structures of Vascular Plants 777 



Fig. 15.1— Subdividing of reproductive organs: A and B, anther of lily; C and D, 

 ovary of lily; E and F, mounted embedded blocks of anther and ovary, respec- 

 tively; G, transverse disk sliced from young fruit of small-fruited variety of tomato; 

 H and /, silique of Matthiola; J, kernel of corn sliced longitudinally; A', center piece 

 of kernel containing essential parts of embryo; L, embedded kernel mounted for 

 sectioning longitudinally. Trimmed edge of paraffin block produces a notched 



ribbon as in Fig. 6AA. 



especially the Easter lilies as well as L. speciosum and L. iimbellatum, 

 have extremely high pollen sterility, and the finished preparations 

 show both nicely preserved pollen grains and shriveled microspores. 

 However, such preparations are useful for illustrating pollen abortion. 

 Lilium regale, L. tenuifoliiim, and L. tigrinum are particularly recom- 

 mended for the study of pollen formation. The first two species have 

 a high ratio of normal pollen, whereas only some strains of the last 

 species are satisfactory. 



For more critical fixation of microspore and pollen nuclei than 

 is afforded by FA A, use the methods recommended for prophases. 

 The somatic division of the microspore nucleus occurs over a brief 



