358 



METHODS IN PLANT HISTOLOGY 



the sporogenous cells have not yet begun to round off into spore 

 mother-cells, it is sufficient to remove the perianth, retaining just 

 enough of the receptacle to hold the stamens in place. Transverse sec- 

 tions show the six stamens and also the young ovary. After the spore 

 mother-cells have begun to round off, each stamen should be removed 

 so as to be cut separately. In securing the desirable stages showing the 

 division of the mother-cell into microspores, much time and patience 

 will be saved by determining the stage of development before fixing 



Bract 

 Corolla 



•Corolla 



Corolla 

 Stamen 



- Bract 

 ^;; Youn^ flowers 



Corolla 



,'Stamen 

 (Microsporophyll) 



^^ Carpel 

 '(Megaspomphyll) 



Calyx 

 (Pappus) 



Fig. 126. — Erigeron philaddpliicus: floral development, .-l and B X3.5; C, D, E, and F X 150. 

 From Chamberlain's Elements of Plant Science (McGraw-Hill Book Co., New York). 



the material. Mitosis is more or less simultaneous throughout an an- 

 ther. Long anthers are particularly favorable, since they may show a 

 very closely graded series of the various phases of mitosis. An anther 

 of Lilium may show mother-cells with nuclei in synapsis at the top, 

 while the mother-cells at the bottom have reached the equatorial plate 

 stage of the first division; or, the mother-cells at the top may show 

 the first division, while those at the bottom show the second. Deter- 

 mine the stage by examining a few mother-cells before fixing. 



From what has been said, it is evident that longitudinal sections 

 should be cut to show mitosis. Transverse sections should be cut to 

 show the general structure of the anther. It is not necessary to cut the 



