ALBUGO PORTULAC& OR A. CANDIDA. 65 



a. The shape of the zoospores, and the pair of bright 

 spots in each. 



b. Study the movement. 



c. Notice the pair of delicate vibratile cilia, by means of 

 which the movements are effected. Stain with iodin 

 and the cilia can be seen more easily. Note their 

 length. 



d. The color imparted to the zoospores and their cilia by 

 the iodin. 



e. Draw some zoospores, and also one or two conidia 

 which have not discharged zoospores, and one or two 

 empty ones. 



II. SEXUAL REPRODUCTION. 



With a dissection or a properly stained section of a specimen 

 containing oospores, observe: 



1. The numerous globular bodies, distinct from and lying 

 in the cells of the host, the oogonia. 



2. Accompanying them, and stained the same color, smaller 

 rounded or elongated bodies, the antheridia. 



3. The way in which the oogonia and antheridia arise from 

 the hyphas. 



4. In some of the oogonia, a globular mass of granular proto- 

 plasm, not completely filling the oogonium, the oosphere. 



5. A slender tube passing from the antheridium to the 

 oosphere, the fertilizing tube: usually difficult to demon- 

 monstrate. 1 Draw. 



6. The development of oospores from oospheres as shown 

 by the various stages in which they have been killed. 



1 It has been shown that the fertilizing tube brings nuclei into the 

 oogonium and that these unite with a corresponding number of nuclei 

 within the oospore. See figures in articles by F. L. Stevens on "The 

 Compound Oospore of Albugo Bliti," Bot. Gaz. 28: 149 and 225; also 

 "Gametogenesis and Fertilization in Albugo," Bot. Gaz. 32: 77, 157, 

 and 238. 



