ILLUSTRATIVE STUDIES 249 



include sporangia in all stages of development, and treat them 

 as described under Cytological Methods, page 257. Stain with 

 Flemming's triple stain. Study with -^^ or ^V oil immersion 

 objective (see page 277 for method of use). Search for all 

 phases of nuclear division in grandmother and mother cells 

 of the spores, and compare with Figs. 123 and 128. Make 

 drawings to show different stages of sporangial development. 

 These should follow the differentiation of sporangium wall, 

 tapetum, and sporogenous tissue, and the segregation of spor- 

 ogenous tissue into single cells or groups of cells, and the forma- 

 tion and migration of the tapetal plasmodium. The fate of the 

 Plasmodium as the spores come to maturity should likewise be 

 followed. 



2. Make cultures of fern spores as described on page 323. 

 Make drarwings to show spores in process of germination as 

 shown under high powers. 



3. Mount mature prothallia under a coverglass in a drop of 

 water. Draw as seen under low power, and study antheridia 

 and archegonia with a high power. Now cut out portions of 

 prothallia bearing antheridia and archegonia, put them in a 

 drop of water on a glass slip, and tease them out under a dis- 

 secting lens, so as to separate as nearly as possible the antheridia 

 and archegonia from the rest of the tissue. Look for sperm 

 and egg cells in situ under the oil immersion objective. A more 

 satisfactory study of the gametes can be made from sections 

 of prothallia prepared as described under Cytological Methods. 

 Make drawings. 



4. Make preparations by cytological methods of anthers of 

 hlies, Tradescantia, Podophyllum, etc., in different stages of 

 development. Stain with Flemming's triple stain. If tips of 

 the anthers are cut off before fixation the fixative will penetrate 

 more siurely and quickly. Care must be taken to have the series 

 begin with anthers so young that division of the grandmother 

 cells has not yet taken place. Preliminary tests can be made by 

 teasing out anthers in gentian violet (p. 304) and soon replacing 

 the stain with water or dilute glycerine. 



