68 



RELATIONS OF PLANTS TO WATER 



105. Reactions of Plasmodia to Water; Hydrotropism. A 



naked mass of protoplasm offers some experimental features of' 



advantage over those of a 

 vegetable structure encased 

 in cellulose membranes. 

 The plasmodial forms of 

 myxomycetes may be found 

 in the spring, summer and 

 autumn on decaying logs ; 

 leaves, and stumps in for- 

 ests, or they may be 

 grown from spores of Tri- 

 chia, Arcyria, Stemonitis, 

 Didymium or other con- 

 venient forms. Plasmodia 

 collected in a forest may be 

 preserved and taken into 

 the laboratory by lifting a 

 fragment of the material on 

 which they are growing, 

 and placing in a jar or 

 closed tin box. Spores may 

 be germinated on pieces of 

 the material on which they 

 were grown in a moist 

 chamber at temperatures of 

 20 to 2 5 C. 



Cut a piece of filter paper 

 the size of a microscopic slide and saturate it in water, then lay it 

 on a slide. Now coat a section at one end inclusive of about 

 three sq. cmm. with liquefied gelatine. Transfer a plasmodium 

 to the filter paper about the center of the slide. Place the pre- 

 paration in a small moist chamber, ventilated in such manner 

 that the filter paper will dry slowly through a period of several 

 hours or a day. The moisture will be retained longer by 



Fig. 28. Apparatus for the demonstration 

 of hydrotropism of roots, h, h, wide-mouthed 

 bottle, s, sand, kk, seedlings, p, showing 

 arrangement of filter paper, tr, tr, openings 

 in dish, w, w, curving roots. After Molisch. 



