772 Bofanicai Microtechnique 



period and is seldom encountered. The monoploid (hai)loid) chromo- 

 some complement is intercstinj^ and deserves carelul staining when 



found. 



Lily ovary is by far the most commonh used subject for teaching 

 the development of the ovule and female gametophyte. The objection 

 to lily is that the nuclear history of the embryo sac differs from the 

 condition in corn, the legumes, and other common crop plants. How- 

 ever, lily ovary and its parts are large, the parallel seriation of the 

 numerous ovules makes sectioning productive, and slides ol the 

 earlier stages, up to cjuartet formation, can be made economically in 

 quantities (Figs. 11.4, 15.4, 15.5). Chrome-acetic has long been a 

 favorite fluid for this subject, and formulas 0.5-0.5 and 0.3-0.70 are 

 excellent for the smaller sporocytes (Fig. 11.3), but the results are 

 rather uncertain with fully expanded sporocytes and subsequent 

 stages. Bouin's solution has been used extensively, but the results are 

 extremely variable. Figure 11.4^ shows a typical Rouin image that 

 is all too common. The rims of the integuments often show a highly 

 wrinkled and collapsed condition. The condition of the sporocyte 

 and integuments after embedding can l^e determined accuratelv in 

 a melted strip of paraffin ribbon. The proportions of ingredients in 

 the original Bouin formula have been rather rigidly accepted by most 

 users, but it is not improbable that superior results could be obtained 

 with carefully determined variants of the formula. 14ie author has 

 obtained some excellent results by using propionic instead of acetic 

 acid as suggested by johansen (1940). 14ie quality of the fixation 

 is im))ro\('d if the jjerfectly fresh ovaries are cut into thin disks. 



1 he most consistent results for all stages have been obtained with 

 the Allen-Bouin modifications, especially 11 and 111 (fable 3.2). 

 A closely graded alcohol-xylene or acetone-xylene series can produce 

 excellent results (Fig. 11.1 d) . l)ut failures are frequent. 1 lie glycerin- 

 evaporation method, the dioxan series or TEA are nuich more re- 

 liable. 1 he (onteiUs of the matinc emhiNo sac are apparent 1\ highly 

 fhiid and parti( iilai ly dillicult to preserve without excessi\e plas- 

 molysis, l)ut Allen-Bouin II usually yields adequate fixation. 



Staining sections of young ovaries i)rior to meiosis is one ol the 

 easiest tasks. A simj^le hemalum stain witli or wiihoiu cixtlnosin is 

 adecpiate for elementary classwork. iron liematoxvlin and safianin- 

 fast green yield brilliant preparations. I'he meiotic aiul gamelophylic 

 division figures and nuclei should l)e stained with iron luinatoxylin, 

 safranin last greiii or safranin-geniian \ iolet. Ihe last (ombinaiion 

 and the triple slain show the s|)in(!le libers exceptionally will. 



