30 ULOTHRIX. 



soon after being placed in water. Fresh material may 

 usually be made to reproduce itself by keeping it in a 

 shallow dish and placing the dish in the dark. Main- 

 taining an even temperature and slowly increasing the 

 density of the liquid tends to induce zoospore formation 

 in this as well as several other Algae. Reproductive 

 bodies when formed in such places are set free after the 

 material has been in the light for an hour or two. 



LABORATORY WORK. 



GROSS STRUCTURE. 



Carefully remove some of the plants from their support and 

 observe how firmly they are attached. Place a small mass in 

 a watch-glass, and observe: 



1. The color as compared with that of the other plants studied. 



2. Whether plants are enclosed in jelly. 



3. The feel of the mass. 



4. The approximate length of single filaments. 



MINUTE STRUCTURE. 



I. THE NUTRITIVE PLANT BODY. 



With a few plants mounted on a slide, under the low power 

 note: 



1. The size and form of the cells. 



2. Whether they are held together as in Nostoc and Oscillatoria. 



3. Any peculiarities of the basal and apical cells. 1 

 With the high power observe : 



4. The form and position of the plastid in each cell. 



5. Whether the basal " holdfast" contains a chloroplast. 2 



1 If the ends are found to consist of broken cells, search for sound 

 specimens. 



2 In most cases the "holdfast" is injured in obtaining the material, 

 consequently it may be impossible to find a good specimen. 



