32 PRACTICAL BOTANY. 



It is perhaps easier in these plants than in any others to trace 

 the successive, stages of development of the archegonium : this 

 may be done by cutting sections, similar to those above described, 

 from young female receptacles, and noting first those archegonia 

 which are situated nearest to the stalk ; these should then be 

 compared with those further removed from it, which will be 

 found to represent successively older specimens : thus the 

 several stages of development may be traced even in a single 

 specimen, and they should be carefully compared with the 

 description and figures given in the standard text-books (e.g 

 Goebel, Outlines of Classification, Eng. Ed. pp. 150, 162). The 

 attempt should further be made to observe the actual rupture of 

 the neck of the archegonium, by preparing sections of the female 

 receptacle, mounting dry ; then, having found a suitable arche- 

 gonium, add a drop of water, when the canal cells and ventral 

 canal cell may be seen to be suddenly extruded on rupture of the 

 apex of the neck. 



XV. Keep some specimens of Marchantia, having 

 mature male receptacles, protected for some days from 

 access of water from above : then place a drop of water 

 on the upper surface of a receptacle, and after a short 

 time transfer it to a glass slide, and examine under a 

 high power : there will then be seen numerous motile 

 antherozoids of elongated, slightly curved form, and 

 they are kept in active motion by two cilia attached to 

 the anterior end. In order to make them clearly visible 

 they should be killed and stained by adding a small 

 quantity of iodine solution, or of osmic acid. 



XVI. Add a drop of water containing living anthero- 

 zoids to a fresh preparation of a female receptacle con- 

 taining mature archegonia : note the directive influence 

 of the archegonia in attracting the antherozoids to the 

 neck, which they enter, and are lost to sight in the 

 mucilage which fills it. 



