50

SIPHONED.

Additional evidence in favour of the influence exerted bythe horns consists in the fact of the capsules or seed-vesselsbeing either perforated or prolonged into a short tube, just atthe place where it comes in contact with the horn. This aperturemay fairly be presumed to be intended to facilitate the admissionto the spores of the granular matter discharged by the horns.

Allusion has already been made in the Introduction to thepowers which many Conferva possess of resisting low degreesof temperature. The spores of the different species ofVaucheria would appear to be endowed with this power to aremarkable extent. “ In spite of all my precautions, thefrost of winter reached the water of my vase, and my grainsbecame enveloped ( engagees ) in very thick ice. They remainedthus until the period of the thaw, that is to say, duringfifteen days, and when they reappeared, I believed them atfirst to be too much injured to hope for any success; but Icalled to mind very opportunely the experiments of Spallan-zani upon the different degrees of cold which seeds wouldbear, without losing in consequence the faculty of germination;and well convinced that the Conferva exposed to the openair had not been more fortunate than mine, I resolved notto abandon my observations.” The observations were con-tinued ; and, as states the text, the grains germinated, to theinfinite delight of Yaucher,

This faculty of resisting cold is bestowed upon the Vau-cheria and many Conferva, and especially upon their seeds,with the evident design of guarding against the extinction ofthe species, which would be almost certain to occur upon thefreezing up of the waters of the ditches in which they areusually found. The power also which these plants, and es-pecially their seeds, retain of sustaining high degrees of tem-perature, is scarcely less remarkable, and is doubtless im-parted to them with a similar provident intention. Thispower in the case of the spores is to be explained by referenceto the compact capsule which surrounds them, and whichprevents the evaporation of the interior moisture. Anotherprecaution adopted by nature to guard still further againstthe risk of the extermination of any species, is the factthat very many Conferva (the Vaucheria included), and