770 Botanical Microtechnique 



vidual flowers, trim the end of the closed perianth, and kill in FAA 

 for gross study or in the fluids recommended for lily. Flowers of 

 tomato also are excellent for advanced workers. 



THE ANTHER AND OVARY 



Microsporogenesis can be studied satisfactorily in the lily. The 

 structure of the anther and sporogenous tissues are also shown well 

 (Fig. 15.2). Whether meiosis in the anther is demonstrated with 

 microtome sections or smears depends on facilities for the production 

 of enough slides for class use. Slides of adequate quality for elemen- 

 tary classes can be produced in quantity by sectioning (Fig. 15.3 «), 

 but smears are far superior for critical details (Fig. 15.3 /;) . For 

 elementary work, the essential and more ob\ious features of meiosis 

 can be demonstrated with paraffin sections from a series of anthers 

 beginning with anthers 2 mm. long up to anthers that are just 

 beginning to show color. Ascertain the stage by means of acetocarmine 

 smears and handle the successive age classes in separate bottles. This 

 saves much time in locating desired stages for sectioning. Subdivide 

 young premeiotic anthers transversely into pieces not over 2 mm. 

 long (Fig. 15.1 A, B) . The excellence of fixation is influenced h\ the 

 degree of subdivision. Good fixation can be obtained by slicing anthers 

 into disks less than 1 mm. thick while holding them under the killing 

 fluid, Allen-Bouin II. This fluid preser^'es the sporocytes and meiotic 

 chromosomes well enough for elementary teaching (Figs. 15.2, 15.3 rt). 

 The anther pieces cannot be cut nuich shorter than 2 to 3 mm. because 

 the sporocytes are loose in the anther at this stage. The chromosomes 

 are superbly stained by iron hematoxylin, gentian violet-iodine, and 

 safranin-fast green. 



The advanced worker who wishes lo demonstrate ihe intimate 

 stiuduic ol the chromosome during meiosis should explore the raj)idly 

 exjianding literature on smear methods, select a species on Avliidi 

 to work, and strive to perfect his techni(|ue until he can demonstrate 

 the structures described by investigators of the subject (Fig. 15.3 /;). 



The dyad condition and second or ecjuational division are of very 

 short duration in lily, and will i)e lound in material selected and 

 j)repared by the loicgoing methods. The quartet (tctiad) and micro- 

 spore stages are of long duration, present during liu- long period of 

 expansion of the llowci bud. until the aiuhers begin to color. For 

 general purposes it is adequate to kill the eniiie anther; FAA yields 

 surprisingly good results. Test each species by means of whole mounts 

 before making a {olUctioii lot this stage. Man\ (uliixatcd lilies, 



