PORELLA. 93 



2. The leaves; note the way in which they are attached to 

 the stem, the number of rows, their positions, and their 

 arrangement at the tips of branches. 



3. Rhizoids; their number and position. 



4. Draw. 



MINUTE STRUCTURE. 



I. VEGETATIVE STRUCTURE. 



Mount two or three of the leaves and observe: 



1. General structure, thickness, arrangement of plastids, 

 presence or absence of epidermis and midrib. 



2. The way in which the leaves join the stem. 

 Mount some of the rhizoids, and observe: 



3. Their general structure; compare with the rhizoids of 

 Marchantia. 



4. Draw. 



II. REPRODUCTIVE STRUCTURE. 



1. Select branches on the tips of which the leaves have 

 formed close tufts, carefully dissect away the leaves and 

 search for archegonia * in different stages of develop- 

 ment. Draw, showing archegonial base, venter, neck, 

 neck canal cells, and egg. 



2. On other branches, having leaves more regularly imbri- 

 cate than the vegetative ones, search for the antheridia, 

 each made up of a long stalk bearing a spherical body in 

 which sperms are formed. It is frequently possible also 

 to observe good stages in the development of the anthe- 

 ridia. Draw. 



3. On old archegonial branches find the sporophytes, each 

 bearing a general resemblance to an antheridium. Search 



1 Specially sectioned and stained preparations cut parallel to the 

 stem of the branches will be found advantageous in studying archegonia, 

 antheridia, and sporophytes. 



