190 PRACTICAL BOTANY 



a. Branches with a relatively thin stalk, bearing a terminal 

 disk with crenate margin, and having numerous dot-like 

 markings on the upper surface : these are the male-branches, 

 having the antheridia on their upper surface. 



b. Branches, also with thin stalks, bearing a terminal star 

 about \ inch to \ inch in diameter : these are the female 

 branches, which produce the archegonia on their under surface, 

 and ultimately the sporogonia and spores. 



II. Remove a thallus carefully from the soil, and wash with 

 water, taking care not to injure it : examine the organs on its 

 lower surface with a pocket lens, and note especially 



1. The numerous rhizoids or root-hairs, attached chiefly to 

 the central midrib. 



2. The amphigastria, white or purple lamellae attached to the 

 lower surface of the thallus, and most clearly seen in the regions 

 near the apex, where they are closely aggregated so as to 

 protect the young tissue. 



B. MICROSCOPIC OBSERVATIONS. 



III. Cut transverse sections of the vegetative thallus of 

 Marchantia, avoiding at first the cups bearing the gemmas, and 

 the sexual branches. It is easier to use material hardened in 

 alcohol, and to embed it in paraffin, or to hold it between pieces 

 of pith : but if sections be cut from fresh green material the 

 presence of chlorophyll will be found to be an advantage in 

 distinguishing the tissues. Mount some sections in weak 

 glycerine, others in chlor-zinc-iodine, or in iodine solution : 

 examine under a high power, and, starting from the upper 

 surface, observe 



a. The superficial layer, or so-called " epidermis," consisting 

 of a continuous layer of cells of small size which contain chloro- 

 phyll : the continuity of the layer is broken here and there by 

 the so-called " stomata " : these, however, differ from the true 

 stomata of the higher plants in the mode of their development. 

 This layer may be seen to be attached to the lower-lying tissues 

 at points between the " stomata," and the lines of attachment 



