BRYOPHYTES—HEPATICAE 
231 
B 
The Thallus.— In many cases it will not be necessary to make a 
special preparation for the study of the thallus, since preparations of 
antheridia, archegonia, or sporophytes may include good sections of 
vegetative portions. This is particularly true of forms like Riccia, 
where the various organs are not raised above the thallus. In forms 
like Marchantidj where the antheridia, archegonia, and sporophytes 
are borne upon stalked receptacles, it is better to make separate 
preparations to show the structure of the mature thallus. Sections 
intended to show the structure of the mature thallus should be 15 to 
25 fjL in thickness, but sections to show the growing point and develop¬ 
ment of the thallus 
should not be thicker 
than 10 fjL. The apical 
region of the Junger- 
manniaceae (Figs. 65, 
66) affords an excellent 
opportunity for study¬ 
ing the development of 
the plant body from a 
single apical cell. If 
mixtures containing 
osmic acid are used for 
fixing, there may be 
difficulty in the staining, even after using peroxide of hydrogen. 
Chromo-acetic mixtures, without osmic acid, are better for the 
apical region. Chromo-acetic acid, followed by Delafield’s haema- 
toxylin, is good for the apical cells and developing regions, but a 
light counter-stain with erythrosin improves preparations of the 
mature thallus. Safranin, with light green, or safranin with crystal- 
violet, will give clear views of the growing region. The latter combi¬ 
nation is particularly good for forms like Pellia , where even the apical 
cell is more or less vacuolated, since it not only brings out the cell 
walls, but stains plastids and other cell contents (Fig. 66). The 
chloroplasts and leucoplasts are well differentiated by this stain. 
After corrosive sublimate-acetic, a vigorous staining in a mixture of 
acid fuchsin and iodine green often brings out the walls very sharply. 
After corrosive sublimate-acetic the material may be stained in bulk 
with alum cochineal or alum carmine, thus giving fairly good prepara¬ 
tions and saving considerable labor. 
Fig. 65. —Ptilidium ciliare: A, longitudinal section, 
and B, transverse section of the apical region of the leafy 
gametophyte. Fixed in chromo-acetic acid and stained in 
Delafield’s haematoxylin. X420. 
