VAUCHERIA SESSILIS. 47 



LABORATORY WORK. 



GROSS STRUCTURE. 



1. Study the general appearance of the mat of plants as they 

 rest on earth or in water. 



2. Note whether they are entirely outside the earth. 



3. Note whether the growing tips have any definite position 

 relative to the light. 



Float out some of the plants in a watch-glass, and by use of 

 the hand-lens note: 



4. Branching of plant body. 



5. Whether any small dark bodies oogonia in which oospores 

 are found can be seen at the sides of plants. Even when 

 present they cannot always be seen with the hand-lens. 



6. Whether there are large, free, green, swimming spores, 

 the zoospores. 



MINUTE STRUCTURE. 



I. VEGETATIVE CHARACTERS. 



Carefully remove the earth from a few plants and mount. 

 With either low or high power, as the case may require, observe: 



1. The length, diameter, and branching. 



2. Absence of cross cell-walls separating the protoplasm into 

 the ordinary cells. It is a ccenocyte. Examine specially 

 stained specimens. 



3. Position, form, and abundance of chloroplasts. 



4. Parts of some plants which have no chloroplasts. Ac- 

 count for their absence. 



5. The method of formation of new chloroplasts, as shown 

 within actively growing plant-tips. 



6. Make drawing illustrating the structure of the plant body. 



