The motile force is imparted to the gonidium by dense rows of waving cilia with which it is completely surrounded. Owing to their rapid vibration, it is almost impossible to distinguish them while the spore is in active motion, but their effect is very plainly seen on adding colored pigment particles to the water. By subjecting the cilia to the action of iodine, their motion is arrested, they are stained brown, and become very plainly visible.

After the gonidium comes gradually to a rest its cilia soon disappear, it becomes perfectly globular in shape, the inclosed granules distribute themselves evenly throughout its interior, and after a few hours it germinates by throwing out one, two, or sometimes three tubular prolongations, which become precisely like the parent filament (Fig 2).

Eminent English authorities have advanced the theory that the ciliated gonidium of Vaucheria is in reality a densely crowded aggregation of biciliated zoospores, similar to those found in many other confervoid algae. Although this has by no means been proved, yet I cannot help calling the attention of the members of this society to a fact which I think strongly bears out the said theory: While watching a gathering of Vaucheria one morning when the plant was in the gonidia-forming condition (which is usually assumed a few hours after daybreak), I observed one filament, near the end of which a septum had formed precisely as in the case of ordinary filaments about to develop a spore. But, instead of the terminal cell being filled with the usual densely crowded cluster of dark green granules constituting the rapidly forming spore, it contained hundreds of actively moving, nearly transparent zoospores, and nothing else. Not a single chlorophyl granule was to be seen. It is also to be noted as a significant fact, that the cellulose wall was intact at the apex, instead of showing the opening through which in ordinary cases the gonidium escapes.

It would seem to be a reasonable inference, I think, based upon the theory above stated, that in this case the newly formed gonidium, unable to escape from its prison by reason of the abnormal strength of the cell wall, became after a while resolved into its component zoospores.

Wonders Of Reproduction

I very much regret that my descriptive powers are not equal to conveying a sufficient idea of the intensely absorbing interest possessed by this wonderful process of spore formation. I shall never forget the bright sunny morning when for the first time I witnessed the entire process under the microscope, and for over four hours scarcely moved my eyes from the tube. To a thoughtful observer I doubt if there is anything in the whole range of microscopy to exceed this phenomenon in point of startling interest. No wonder that its first observer published his researches under the caption of "The Plant at the Moment of becoming an Animal."

Formation Of Other Spores

The process of spore formation just described, it will be seen, is entirely non-sexual, being simply a vegetative process, analogous to the budding of higher plants, and the fission of some of the lower plants and animals. Vaucheria has, however, a second and far higher mode of reproduction, viz., by means of fertilized cells, the true oospores, which, lying dormant as resting spores during the winter, are endowed with new life by the rejuvenating influences of spring. Their formation may be briefly described as follows:

When Vaucheria has reached the proper stage in its life cycle, slight swellings appear here and there on the sides of the filament. Each of these slowly develops into a shape resembling a strongly curved horn. This becomes the organ termed the antheridium, from its analogy in function to the anther of flowering plants. While this is in process of growth, peculiar oval capsules or sporangia (usually 2 to 5 in number) are formed in close proximity to the antheridium. In some species both these organs are sessile on the main filament, in others they appear on a short pedicel (Figs. 3 and 4). The upper part of the antheridium becomes separated from the parent stem by a septum, and its contents are converted into ciliated motile antherozoids. The adjacent sporangia also become cut off by septa, and the investing membrane, when mature, opens: it a beak-like prolongation, thus permitting the inclosed densely congregated green granules to be penetrated by the antherozoids which swarm from the antheridium at the same time.

After being thus fertilized the contents of the sporangium acquire a peculiar oily appearance, of a beautiful emerald color, an exceedingly tough but transparent envelope is secreted, and thus is constituted the fully developed oospore, the beginner of a new generation of the plant. After the production of this oospore the parent filament gradually loses its vitality and slowly decays.

The spore being thus liberated, sinks to the bottom. Its brilliant hue has faded and changed to a reddish brown, but after a rest of about three months (according to Pringsheim, who seems to be the only one who has ever followed the process of oospore formation entirely through), the spore suddenly assumes its original vivid hue and germinates into a young Vaucheria.

Charm Of Microscopical Study

This concludes the account of my very imperfect attempt to trace the life history of a lowly plant. Its study has been to me a source of ever increasing pleasure, and has again demonstrated how our favorite instrument reveals phenomena of most absorbing interest in directions where the unaided eye finds but little promise. In walking along the banks of the little stream, where, half concealed by more pretentious plants, our humble Vaucheria grows, the average passer by, if he notices it at all, sees but a tangled tuft of dark green "scum." Yet, when this is examined under the magic tube, a crystal cylinder, closely set with sparkling emeralds, is revealed. And although so transparent, so apparently simple in structure that it does not seem possible for even the finest details to escape our search, yet almost as we watch it mystic changes appear. We see the bright green granules, impelled by an unseen force, separate and rearrange themselves in new formations. Strange outgrowths from the parent filament appear.

The strange power we call "life," doubly mysterious when manifested in an organism so simple as this, so open to our search, seems to challenge us to discover its secret, and, armed with our glittering lenses and our flashing stands of exquisite workmanship, we search intently, but in vain. And yet not in vain, for we are more than recompensed by the wondrous revelations beheld and the unalloyed pleasures enjoyed, through the study of even the unpretentious Vaucheria.

The amplification of the objects in the engravings is about 80 diameters.

[1]Read before the San Francisco Microscopical Society, August 13, and furnished for publication in the Press.