*4 



HARD WICKE ' S S CIENCE- G SSI P. 



vegetable cell, it being sufficient in some cases to 

 mount a portion of tissue in water, when the nucleus, 

 and parietal sac of transparent protoplasm investing 

 the interior of the cell wall are plainly observed. 

 Pig. 13 represents a living hair from the petal of 

 Viola tricolor thus prepared ; it will be noticed that 

 the nucleus lies embedded in a viscous mass of pro- 

 toplasm from which protoplasmic streamers or threads 

 ■extend to the parietes of the cell, being surrounded 

 by the cell-sap in the unoccupied spaces or vacuoles. 

 Protoplasm, when killed by certain re-agents, assumes 

 the appearance of a dense, brownish, granular mass 

 lying loose in the interior of the cell (Fig. 16). Most 

 of its structural peculiarities are by this process 

 ■destroyed, indeed in one sense it is no longer pro- 



SFig. 16. — Parenchymatous cell from bulb of Allium cepa, the 

 protoplasm contracted by acetic acid. (Much magnified.) 



toplasm at all, being deprived of the only essential 

 characteristic which distinguishes it from any other 

 nitrogenous or albuminous compound. The shrinking 

 of protoplasm from the cell wall would seem to be 

 an osmotic phenomenon. I have observed that the 

 addition of a simple saccharine solution will cause 

 the protoplasm of the common Alga Cladophora to 

 shrink, and the mere application of water will 

 coagulate the contents of the embryo-sac of Viola 

 tricolor. Acetic acid, or alcohol, contract the pro- 

 toplasm of tissues macerated in them for a short 

 time ; the acetic acid contained in ordinary vinegar 

 shows the effect very well. 



The motile power of protoplasm is of course very 

 wonderful and interesting ; but in the majority of 

 cases it is but slow and ill-defined. The "streaming " 

 arrangement of granules and particles in many cells, 

 would seem to be indications of an imperceptible 

 movement, but the most imposing instances are 

 those of the locomotion of naked masses of pro- 

 toplasm. In order to witness this very remarkable- 



sight, I here give practical directions from experience : 

 a flea {Pulex irrilans), newly killed, is to be placed 

 in a wine-glass full of water in a warm place ; and 

 in course of a day or two the insect will be enveloped 

 in a white flocculent gauze : this flocculence is a 

 luxuriant tuft of the plant Saprolegnia ; now remove 

 the insect bodily to a glass slip, and mount in water 

 for the microscope. The club-shaped, or clavate 

 ends of the hyphce, will be observed in various 

 phases of development ; many will simply consist 

 of a pale granular cord of protoplasm, enveloped by 

 a transparent membranous cell- wall, but in some, a 

 septum will have been constructed across the tubular 

 hypha, thus detaching a mass of protoplasm destined 

 to form a sporangium, and this protoplasm will be 

 found to have resolved itself into a vast number of 

 small globular or oval portions : let such an hypha 

 be particularly watched : probably within a few 

 minutes the apex of the sporangium, or hypha, will 

 dissolve, meanwhile the globes of protoplasm within 

 the hypha seem agitated like a swarm of bees, they 

 seem nervously to crowd and jostle against each 

 other, until they are suddenly released, when, with 

 infinite grace they strike out their fine cilia and steer 

 through the water in much the same fashion as many 

 infusoria. Indeed these zoospores, as they are termed, 

 if their origin were unknown, could not be distin- 

 guished by any known characteristic from so-called 

 infusoria. 



While protoplasm is generally hyaline or faintly 

 granular in appearance, there are many notable 

 exceptions. Chlorophyll is generally considered to 

 be a coloured species of protoplasm, the zoospores 

 of crimson Algce or Floridea; are coloured, and the 

 oospheres of our common Fuci are orange-red, or 

 brown. Moreover the protoplasm of pollen cells 

 is generally densely granular, partly from the presence 

 of starch, and oil-drops. Take some pollen-cells from 

 the anther of Viola tricolor and mount in water ; each 

 cell will, speedily swell, becoming globose by the 

 absorption of water by osmosis : presently the pollen- 

 cell will violently discharge its protoplasm, a mass 

 of almost opaque granules forming beautiful festoons 

 in the liquid. 



I have observed that the nuclei in our common 

 Orchidaceous plants very easily deliquesce into large 

 granules ; they may be well examined in the epidermal 

 cells. 



A most remarkable feature of protoplasm is its 

 extreme sensitiveness to external impressions or 

 stimuli : even such feeble vibrations as those of the 

 luminiferous ether, or light are competent to arouse 

 it from a nascent to an active condition, e.g., the 

 elaboration of chlorophyll. It might therefore be 

 expected that the more powerful undulations of heat 

 would profoundly affect it, as is the fact ; indeed heat 

 not only produces an invisible molecular activity in 

 protoplasm, but we know that visible protoplasmic 

 movements are affected by it before our very gaze 



