PRACTICAL BOTANY 



1. The normal structure of the main thallus. 



2. The club-shaped antheridial branches, often associated 

 together in groups : each consists of 



a. A unicellular pedicel, by which it is attached to the thallus. 



b. A central linear series of cells, which is almost entirely 



hidden by 

 c Numerous, closely aggregated, and small antheridial cells. 



Mount specimens of antheridial branches from fresh living 

 material in sea-water, and having found an antheridial branch 

 exactly at the period of maturity observe the partial dis- 

 organization of the walls of the antheridial cells and consequent 

 liberation of their protoplasmic contents, without subdivision, as 

 round non-motile spermatia. 



VII. Having recognized a female plant by observations with a 

 lens on specimens taken in late summer or autumn, mount a 

 portion of it in glycerine, and, examining it under a low power, 

 observe 



1. The normal structure of the thallus, which bears 



2. Cystocarps of ovate form : these consist of closely aggre- 

 gated, small-celled tissue : they occupy the same position as the 

 lateral branches in a vegetative thallus. 



3. Compare numerous specimens, and note cystocarps in 

 various stages of development. 



VI 1 1. Embed mature cystocarps of P . fastigiata in paraffin, and 

 cut from them median longitudinal sections : mount in glyce- 

 rine, and observe 



1. The short thick stalk of the cystocarp. 



2. Its wall, consisting of small, closely aggregated cells, and 

 with an opening or ostiole at the apex. 



3. The central cavity, surrounded by the wall, and filled more 

 or less completely, according to age, with elongated, club-shaped 

 cells, having dark protoplasm, and swollen walls ; these are the 

 carpospores. 



The artificial germination of the spores is a matter of difficulty, 

 but a rough idea of the germination of the spores of red seaweeds 

 may be gained by observing the numerous young plants, of 

 various genera and species, which are to be found attached to 

 the outer surface of almost any one of the larger seaweeds. 



