16 



METHODS IN PLANT HISTOLOGY 



There should be a graduate, preferably 50 c.c. or 100 c.c. If the 

 bottles are of uniform size, 50 c.c, 100 c.c., 500 c.c. and 1,000 c.c, the 

 student should soon be able to estimate with sufficient accuracy for 

 making up reagents which do not require extreme accuracy. 



Three or four pipettes, or medicine droppers, will be useful. Occa- 

 sionally, the glass of an ordinary pipette, thrust into a small camera 

 bulb, will save time in drawing off reagents. 



Fig. 12. — -Coil of brass wire holding 15 slides 



SHdes and covers are a constant expense. Many shdes now upon the 

 market are imperfect. Beware of slides which are not perfectly flat. 

 Be skeptical in regard to any claim that slides are already clean 

 enough to use. Of course, there should be no bubbles. "White" shdes 

 are to be preferred to those which appear greenish in the box. For 

 ordinary class work, slides of medium thickness are more serviceable, 

 but for critical cytological work many investigators prefer very thin 

 slides. 



Slides and covers, as you buy them, arc never clean, no matter how 



