200 METHODS IN PLANT HISTOLOGY 



in packing; or, better still, a sheet of cork. At each end nail in a piece 

 of pine half an inch thick and an inch high. Upon these end pieces 

 place a thin piece of pine, thus making a second bottom, which, of 

 course, should not be fastened. A second pair of ends with a third 

 pine bottom nailed to them may rest upon the second bottom. The 

 three bottoms will give a considerable surface upon which the material 

 may be pinned. For most purposes, the specimens are simply allowed 

 to dry, and are then fastened with glue or paste to the bottom of a 

 small box. 



Plasmodia and young sporangia may be fixed in chromo-acetic acid, 

 but staining with iron-alum haematoxylin is likely to be more satis- 

 factory if some osmic acid is added. The solution — 0.7 g. chromic 

 acid, 3 cc. glacial acetic acid, and 7 c.c. 1 per cent osmic acid to 90 c.c. 

 distilled water — will be good for the younger stages of any myxo- 

 mycete. Sections cut easily in paraffin. For general structure, 5 /x is 

 thin enough; but for nuclear detail 3, 2, or even 1 ju will be better. 

 Since the material cuts so easily, this is a good place to practice cutting 

 thin sections. Remember that a good sliding microtome is better than 

 a rotary for very thin sections. 



The safranin, gentian violet, orange combination is good for a study 

 of the general development and for some cytological features, but iron- 

 alum haematoxylin is better for nuclear details. 



Spores of most myxomycetes will germinate as soon as they are 

 thoroughly ripe, and, during the first year, germination is more 

 prompt than in case of older spores. Fresh spores may germinate in 

 half an hour; the time may extend to several hours; spores two or three 

 years old may germinate in three or four days, or may not germinate 

 at all. We have never succeeded in germinating spores which were 

 more than three years old. The longevity is doubtless different in 

 different species. In most cases, spores will germinate in water, if they 

 will germinate at all. For small cultures, the hanging-drop method, 

 described on page 82, may be used. 



Plasmodia may be raised by sowing spores on moist, rotten bark or 

 wood and placing the culture under a bell jar, where the moist, sultry 

 condition favorable to their growth is easily imitated. Plasmodia may 

 be got upon the slide by inclining the slide at an angle of about 15°, 

 with one end of the slide at the edge of the plasmodium, and allowing 

 water to flow very gently down from the upper end of the slide to the 

 lower. The proper flow of water could be secured by dropping water 



