370 PKACTICAL BOTANY 



2. Two involutions of the margin, corresponding to 

 two channels, which traverse the stalk longitudinally : 

 due investigation will show that these are on the 

 morphologically lower face of the stalk. 



3. Rhizoids will be found traversing these channels 

 longitudinally. 



4. The tissues seen in these sections are not clearly 

 differentiated. 



X. Cut median vertical sections through the terminal 

 disk : mount in weak glycerine, and examine first under 

 a low power : observe 



1. The general outline of the section, and especially 

 the attachment of the disk, and the flat upper surface. 



2. The amphigastria and rhizoids attached to the 

 lower surface. 



3. The cavities in the tissue, of two sorts, both 

 opening by narrow mouths on the upper surface 



a. Air-cavities fundamentally similar to those 

 of the vegetative thallus, with a " stoma " 

 above the centre of each, and with chloro- 

 phyll-containing cells as before. 

 Z>. Flask-shaped cavities each containing one 

 anther idium : these also open by a narrow 

 channel on the upper surface of the disk. 

 Look for a single ripe antheridium which has been 

 cut through longitudinally : having found one, examine 

 it in detail under a high power, and observe 



1. The short stalk by which it is attached to the 

 base of the cavity. 



2. The wall of the antheridium, consisting of a single 

 layer of thin-walled cells. 



3. The mother-cells of the spermatozoids of 



