98 TYPE STUDIES 



2. PlurilociUar sporangia or gametangia. These are branches composed 

 of a very large number of small cubical cells, each of which produces 

 one or perhaps two or three two-ciliate elements similar to zoospores, 

 but which are known to be gametes in some forms, conjugating in 

 pairs as in XJlothrix. Trace the development of the plurilocular 

 sporangia from vegetative branches. It should be noted that they 

 are many-celled organs both in structure and origin. 



3. Should zoospores or gametes be discharged from living material, 

 study their movements and then stain with iodine (as described in 

 Sec. 67, B). Note their kidney form and the pair of cilia inserted 

 laterally. 



94. Kelps. Study the morphology of such kelps as may be available, not- 

 ing holdfast, stalk, and blade. Should the blades be in fruit, cut sections in 

 pith to show the one-celled sporangia. 



95. Fucus, the rockweed.* * Fucus vesiculosus is perhaps the 

 most conYenient species for study. Describe its color, consist- 

 ency, and life habits if studied living on the rocks. 



A. Make a habit sketch of a plant, noting : 



1. Its method of branching, thickened midrib, and lateral 

 expanded margin. 



2. The presence of air bladders and swollen tips, called 

 receptacles. 



3. Sunken regions in the receptacles, termed conceptacles, 

 each opening to the exterior by a pore through which 

 protrudes a cluster of delicate filaments, paraphyses. 



4. The flattened vegetative tips with a pit at the end, at the 

 bottom of which lies a group of cells forming the grow- 

 ing point. 



5. The disk-shaped holdfast. 



B. Cut across a receptacle and under l.p. or with a liand lens 

 diagram the distribution of the conceptacles. Note in living 

 material the color of the contents of the conceptacle, whether 

 dark green or orange, and later determine which contain 

 male organs and which female. 



C. Dig out with the point of a scalpel the contents of a con- 

 ceptacle, and mount in water. Study the sexual organs. 



