and always use water that has been boiled.  At the end of six weeks or so the prothallus will perhaps appear, certainly in a week or two more; perhaps from unforeseen circumstances not for three months.  Slowly these will begin to show themselves as young ferns, and most interesting it is to watch the results.  As the ferns are gradually increasing in size pass a small piece of slate under the edge of the bell-glass to admit air, and do this by very careful degrees, allowing more and more air to reach them.  Never water overhead until the seedlings are acclimated and have perfect form as ferns, and even then water at the edges of the pots.  In due time carefully prick out, and the task so interesting to watch is performed.—­The Garden.

* * * * *

THE LIFE HISTORY OF VAUCHERIA.

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

By A.H.  BRECKENFELD.

Nearly a century ago, Vaucher, the celebrated Genevan botanist, described a fresh water filamentous alga which he named Ectosperma geminata, with a correctness that appears truly remarkable when the imperfect means of observation at his command are taken into consideration.  His pupil, De Candolle, who afterward became so eminent a worker in the same field, when preparing his “Flora of France,” in 1805, proposed the name of Vaucheria for the genus, in commemoration of the meritorious work of its first investigator.  On March 12, 1826, Unger made the first recorded observation of the formation and liberation of the terminal or non-sexual spores of this plant.  Hassall, the able English botanist, made it the subject of extended study while preparing his fine work entitled “A History of the British Fresh Water Algae,” published in 1845.  He has given us a very graphic description of the phenomenon first observed by Unger.  In 1856 Pringsheim described the true sexual propagation by oospores, with such minuteness and accuracy that our knowledge of the plant can scarcely be said to have essentially increased since that time.

[Illustration:  GROWTH OF THE ALGA, VAUCHERIA, UNDER THE MICROSCOPE.]

Vaucheria has two or three rather doubtful marine species assigned to it by Harvey, but the fresh water forms are by far the more numerous, and it is to some of these I would call your attention for a few moments this evening.  The plant grows in densely interwoven tufts, these being of a vivid green color, while the plant is in the actively vegetative condition, changing to a duller tint as it advances to maturity.  Its habitat (with the exceptions above noted) is in freshwater—­usually in ditches or slowly running streams.  I have found it at pretty much all seasons of the year, in the stretch of boggy ground in the Presidio, bordering the road to Fort Point.  The filaments attain