A HUNDRED MICROSCOPICAL OBJECTS 231 



36. Antheridia of Chara. — Dissect out antheridial 

 filaments of Chara or Nitella, and mount them in iron- 

 acetocarmine. Open other antheridia, and fix in chrom- 

 acetic-formahn, wash in chrom-acetic, run through the 

 alcohols to 70 per cent, and stain with iron-brazilin. Dis- 

 sect out the stained filaments in immersion oil. Study 

 sequence of stages in the cell divisions (Karling). 



37. Antheridia of Fucus. — Mount the division stages in 

 iron-acetocarmine, with subsequent squeezing out. Try 

 if smears can be well fixed in chrom-acetic-formalin, and 

 stained with iron-brazilin. (This object has been used 

 as a test for good fixation by Chamberlain.) 



38. Origin of Epidermis, etc. — Cut median sections in 

 paraffin of soft stem apices. Use chrom-acetic-formalin 

 and iodine gentian-violet, or iron-hsematoxylin in 70 

 per cent alcohol. Try especially Pelargonium, Zea, Sola- 

 num, Lycopersicum, Mirabilis, and Delphinium. Trace 

 the origin of the leaves from the different cell layers. 



39. Formation of Tissues from Cambium. — Stem of 

 woody dicotyledon in the early summer. Fix small seg- 

 ments, freed from superfluous wood and cortex in chrom- 

 acetic-formalin. Cut in alcohol-glycerin with the sliding 

 microtome. Stain with Mayer's hsemalum and methyl 

 green, and mount in xylol balsam or in immersion oil. 

 The origin of vessels, wood fibers, sieve tubes, bast fibers, 

 etc. is traceable. Tangential sections show most. 



40. Study of Starches. — (a) Mount in water or agar, 

 and examine with water-immersion objective. (6) Mount 

 in immersion oil, and examine by polarized light. Put a 

 large tourmalin or a polarizing calcspar prism near enough 

 to the diaphragm before the source of light not to cut down 

 the aperture of the condenser. Put a small tourmalin over 

 the eyelens. If the tourmalins have plane-parallel 

 sides, the corrections of the microscope are not injured, and 

 the highest oil-immersion objectives maybe used. The tour- 

 malins should be 3 millimeters thick (Beck). The monoc- 

 ular microscope with a silvered prism is best to use, because 

 of polarization by reflection. 



