572 VISIBLE CONSTRUCTIVE ACTIVITY IN PROTOPLASM. 



VISIBLE CONSTRUCTIVE ACTIVITY IN PROTOPLASM. 



Though it is improbable that we shall ever succeed in seeing the micellae of 

 which the organized living portions of plants are built up, and though all attempts 

 to form a picture of these tiny units are only founded upon conjecture and hypo- 

 thesis, still we can follow with our eyes the general operations, the constructive 

 and shaping activity of the protoplasm. 



This formative activity can be most easily observed in the comparatively large 

 protoplasmic bodies of myxomycetes, in their so-called plasmodia; therefore some of 

 the most striking of these processes will now be briefly described. 



The myxomycete Leocarpus fragilis, which commonly occurs on the bark of 

 dry, fallen branches of the Pine, forms a viscous yellow mass, looking deceptively 

 like the spilt yolk of an egg. The dead branch is covered by a thin layer of this 

 substance, in which no particular projections can be recognized. Quite late in the 

 evening Leocarpus can be seen in this plasmodial stage. During the night, how- 

 ever, it rises up in certain places into knobs and warts, and the whole mass then 

 has a coarsely granular appearance. Towards morning, pear-shaped bodies, sup- 

 ported on thin stalks, are produced from these protuberances, which are now no 

 longer viscous, but exhibit a thin dry pellicle. Within, they have become trans- 

 formed into numerous hair-like threads, with black powdery spores lying between 

 the threads. Leocarpus needs about 12 hours for this manifestation, and if one has 

 the patience to observe the mass shaping itself throughout the night, one may 

 actually see how it rises from the substratum, rounds itself off", forms a skin, and 

 assumes the pear-shape form. Dictydium umbilicatum develops its plasmodia in 

 the same way as Leocarpus. The light brown, irregular, flowing mass of proto- 

 plasm gathers itself up into a round cord, which becomes thickened in a club- 

 shaped manner at its upper end, and then spreads out into a delicate net -work 

 with spherical outline. Between the meshes of this net-work the protoplasm 

 separates out into black powdery spores, which are at the mercy of the slightest 

 breath of wind. The slimy protoplasm of Stemonitis fusca, on the other hand, 

 rises up in the shape of numerous closely -compacted strands about 1| cm. long. 

 Each individual strand is divided into a lower, stalk-like portion, and an upper, 

 thick, cylindrical body. This is at first of slimy consistency, but soon becomes dry 

 and divides into a central axis, from which proceed all round an endless number of 

 very fine reticulating threads which break up into thousands of powdery spores, 

 and at the periphery into a very delicate skin, which later on ruptures and allows 

 the spores to fall out. This entire shaping of the protoplasm, with which is con- 

 nected a change of colour from white to purple, is accomplished under the eye of 

 the observer in about ten hours. The protoplasm of Chondrioderma difforme can 

 scarcely be distinguished from that of Stemonitis fusca, and yet how very diff'erent 

 is the form which it assumes as a plasmodium. First, it is massed into a round 

 ball, and in this is separated out an enveloping skin of innumerable single slender 



