FUCUS VESICULOSUS 99 



In attempting to answer this last question recall 

 the habitat of Fucus. 



F. Vegetative Propagation: 



1. Vegetative propagation is accomplished by the 

 breaking off of branches which may float away 

 and become established as new individuals. 



2. Frequently, by a process of regeneration, dwarf 

 branches are formed where portions of the thallus 

 have been torn away. Do you find instances of 

 this in the material at hand? 



G. Sexual Reproduction: 



1. The sexual reproductive organs of Fucus are borne 

 in fertile conceptacles, imbedded in the cortical 

 tissue of the receptacles. In Fucus vesiculosus the 

 conceptacles containing the female organs are on 

 different plants, i.e., the plants are dioecious. In 

 other species they are both on the same plant, while 

 in still other species (e.g., F. edentatus) both kinds 

 of organs are in the same conceptacle. In the two 

 latter cases the plants are monoecious. 



2. The Male Conceptacles: 



(a) Examine a longitudinal section of a male 

 conceptacle, passing through the ostiole. Note 

 the outline of the cavity. Describe its wall. 



(b) Observe the filaments (paraphyses) within the 

 cavity, and describe the length, diameter, 

 shape, and structure of one of them. Do any 

 of these filaments project through the ostiole? 

 Explain the feeling as a receptacle is taken be- 

 tween the thumb and fingers. 



(c) Are the filaments that pass through the ostiole 

 similar to those that do not? On the latter 

 observe the small ellipsoidal organs antheridia. 

 Where and how are they attached? How 



