^474 Journal of Applied Microscopy 



Series II. ARCHEGONIATA. Sub-kingdom, BRYOPHYTA. 



XLIV. (a) Riccia fluitiDis L. Class, Hepaticae. Order, Marchantiales. 

 Family, Ricciaceae. 



This liverwort has a small, linear, dichotomously branched thallus which 

 grows floating in ponds and ditches. It also grows in wet places upon the 

 ground, sometimes in cultivated fields. The plant keeps well along with other 

 hydrophytes in a covered, glass jar of water. 



1. Mount a small thallus or frond (gametophyte) in water and examine 

 under dissecting microscope. Make a sketch of the plant and describe. 



2. Draw a branch of the thallus under low power, showing the air cavities 

 and cellular structure. Note that this thallus is not made of branching or inter- 

 woven filaments, but that it is a true solid aggregate. Most of the thallophytes 

 are either simple or complex linear aggregates. 



3. The aquatic form of this plant is usually sterile. In order to study the 

 sexual organs and sporophyte to advantage, examine prepared slides of Riccio- 

 carpus. 



(b) Ricciocarpus natans (L.) Corda. 



This plant forms a small, obcordate thallus which floats on the surface of 

 ponds and swamps. The individuals are unisexual and develop the reproduc- 

 tive organs in late summer and autumn. 



1. Sketch the living plant under dissecting microscope. Describe. 



2. Under low power draw part of a section from a prepared slide, showing 

 an antheridium. Draw part of a section, showing the archegonium containing 

 the oosphere. 



3. Draw an enlarged archegonium with the spherical sporophyte, contain- 

 ing a wall one layer of cells in thickness, with the spore-mother-cells (sporocytes) 

 lying free in the interior. 



4. From older stages draw spore tetrads and mature spores under high 

 power. 



5. If prepared slides are not at hand, cut freehand sections (with the aid of 

 strips of fresh carrot roots) of male and female plants and draw an antheridium 

 and an archegonium under low power. Also cut sections of a female plant con- 

 taining a sporophyte and some free spores. 



t). Compare the sporophyte with that of Coleochaete and note the beginning 

 of sterilization of the tissue of the sporophyte. 

 Ohio State University. JOHN H. SCHAFFNER. 



