180 



Methods in Plant Histology 



a 



A 



In about 24 hours this not only fixes, but it dissolves the lime with 

 which most species are coated. 



For paraffin sections select the tip of the plant, a piece about 

 half an inch in length. Sections of this may show, not only the large 

 apical cell, but also various stages in the development of antheridia 

 and oogonia. For the development of the plant body from the 

 apical cell and also for early stages in the development of oogonia 



and antheridia, the 

 safranin, gentian-violet, 

 orange combination is 

 excellent; for later 

 stages, especially in the 

 development of the 

 antheridia, iron-haema- 

 toxylin is much better. 

 The antheridium of 

 Chara stains so rapidly 

 that the beginner uni- 

 formly makes poor pre- 



B 



FIG. 41. Chara: A, portion of a branch showing 

 an antheridium, a, and an oogonium, o; X35; B, median 

 longitudinal section of an apical cell; drawn from a 

 preparation fixed in chromo-acetic acid and stained in 

 Delafield's haematoxylin; X225. 



parations. In order to 

 get good preparations 

 of the antheridium, it 

 is necessary to disregard 

 other structures, which 

 will be stained lightly or not at all when the stain is just right in 

 the antheridial filaments. 



If it is desired to mount whole branches showing the antheridium 

 and oogonium in position, as in Fig. 41, use the Venetian turpentine 

 method, staining in Magdala red alone, or in Magdala red and anilin 

 blue. Good mounts showing shield, manubrium, capitula, and fila- 

 ments may be obtained by crushing an antheridium under a cover- 

 glass. For this it is better to stain in Magdala red alone, since any 

 overstaining is easily corrected by exposing the preparation to direct 

 sunlight. 



