134 Practical Plant Biology. 



antheridia and archegonia of Marchantia, of a large number of 

 cells. The structure of the archegonia is very uniform in large 

 groups of the higher plants and differs very strikingly from that 

 of the oogonia of the algae. Hence it is sometimes convenient 

 to speak of the groups of the land flora which are characterised 

 by this special form of female gametangium as the Archegoniates. 

 Marchantia is one of the Archegoniates. 



PRACTICAL WORK. 



Examine the archegoniophores and antheridiophores with a simple lens. 

 Make sketches of them from various aspects, magnifying them 4 or 5 

 diameters. 



Prepare transverse sections of the stalk. Make sketches showing the 

 longitudinal grooves containing the rhizoids. 



Prepare radial vertical sections of the disc of both organs and make 

 sketches illustrating the structure and position of the antheridia and arche- 

 gonia. 



Material collected in May and June will illustrate the development of the 

 antheridia and archegonia. Sections of the antheridiophores will show the 

 mother-cells of the sperms and the production of the sperms. Archegonio- 

 phores at the same time will show the development of the archegonia, 

 fertilisation, and the early stages of the sporophyte. 



If a drop of water is placed on one of these antheridiophores and watched 

 for a few 'minutes with a simple lens, the ejection of the sperms may be 

 easily observed. They appear like minute puffs of milky fluid emitted from 

 the antheridial cavities into drops of pellucid water. 



Material taken later in the year, viz. July to October, shows the various 

 stages in the development of the sporophyte up to the dehiscence or rupture 

 of the sporangium and the emission of the spores from it. The structure 

 and movements of the elaters may be observed microscopically by mounting 

 some of them dry and uncovered on a slide. 



