Plant histology: Myxomycetes





With the exception of a few forms like Fuligo (often found on oak stumps and on oak bark in lanyards), the myxomycetes are small, and are usually overlooked by collectors. A careful examination of rotting logs in moist woods will usually reveal an abundance of these delicate and beautiful organisms. Various species may be found in spring, summer, and autumn. The plasmodia are most abundant just after a warm shower. A couple of days of dry weather will then bring sporangia in abundance. The specimens should be pinned to the bottom of the box for safe carrying. An excellent collecting-box can be made from an ordinary paper shoebox. On the bottom of the box place a thin piece of soft pine, or a piece of the corrugated paper so commonly used 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 or Flemming's fluid. Sections are easily cut in paraffin, and should not be more than 5( in thickness; for nuclear details, sections should not be thicker than 3(. 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.

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 from a pipette, but a less tedious plan is to arrange a siphon so as to secure a similar current. The plasmodium will creep up the slide against the current, furnishing an excellent illustration of rheotropism. Enough plasmodium for an illustration may be formed in two or three hours. Examined under the microscope, the preparation should give an excellent view of the streaming movements of protoplasm.





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