ULOTHRIX. 31 



6. Stain a few plants with a solution of iodin and try to find 

 the nucleus. In case the chloroplast should contain starch 

 it will usually be stained a dark blue by the iodin. The 

 cytoplasm may also be stained and made more easily seen 

 by this process. 



7. Draw a few cells showing details of structure. Also draw 

 the "holdfast," in case one is found. 



II. REPRODUCTION. 



A. VEGETATIVE. 



In connection with the processes of growth the cells divide, 

 thereby increasing the length of the plant. Watch for evi- 

 dence as to whether these elongated plants may break, thus 

 forming two or more plants. 



B. BY SPORES. 1 



Locate some cells in which the protoplasm has been divided 

 into four or more zoos pores, and study the spores, noting: 



1. Their form. 



2. The cilia at the smaller end. How many? 



3. The plastid within the spore. 



4. How the zoospores escape from the cell in which they are 

 formed. 



5. Try to find some of the zoospore-like bodies that are 

 uniting in pairs thus forming sexual spores. 



In a dish of material which has been standing for some 

 days will usually be seen a ring of young plants adhering to the 

 glass at the surface of the water. Remove and mount some 

 of this material Observe : 



6. Spores just beginning to germinate. 



1 Outline is not provided for studying all of the details of reproduc- 

 tion in Ulothrix as those details are given in current text-books, since 

 investigations now being made at the University of Chicago indicate 

 that the text-book accounts are in error. 



