334 THE BIOLOGY OF THE PLAIfT 



raise them in the manner to be described here- 

 after. Place a young prothallium in a drop of 

 water and examine under the low power. What 

 is the shape of the prothallium ? Color ? Look 

 for rhizoids on the lower surface. Are they con- 

 fined to any particular region ? Draw. Examine 

 with the high power. What are the general char- 

 acters of the cells composing the prothallium? 

 What do they contain ? Look for the growing 

 point at the base of the depression in the margin. 

 How do the rhizoids differ from the root-hairs on 

 the fern-plant ? From the rhizoids of Marchantia 1 

 Among the rhizoids look for knob-like bodies, the 

 antheridia and the archegonia. The former 

 may be distinguished in surface view as consisting 

 of a small circular eminence of a single large cell, 

 or of several small ones without any opening be- 

 tween them ; each archegonium usually appears as 

 a ring of four cells surrounding a plainly visible 

 opening, the mouth of the canal. What other dif- 

 ferences can you distinguish between these two or- 

 gans? In case mature specimens are examined, 

 many antherozoids will probabl}' be found swim- 

 ming around in the water. If so, study their move- 

 ments and structure. Note the body of the an- 

 therozoid and the cilia. To what part of the 

 body are the latter attached 1 Are they numerous 

 or few ? Look for the vesicle, which is usually 

 attached to the body. Draw several anthero- 

 zoids. To make out the structure of the arche- 

 gonium, sections of the prothallium should be cut. 

 Successful sections will show an archegonium to 

 consist of a neck — down which runs a canal, 

 whose mouth, was seen in the surface view — 



