of the Spores in Spirogyra. 217 



them. In spite of this difference, however, the young plants 

 produced exhibit exactly the same behaviour in both cases. 



I had conjectured at first that the opposition between the 



anterior and posterior extremities of the spore would be already 



indicated by its position in the filament-cell. All spores of the 



same filament open ordinarily on the same side, so that if 



we call that end of the spore through which the young plant 



emerges, the anterior extremity, all the spores of one filament 



have their anterior ends turned in the same direction (PI. VIII. 



fig. 1 a, b, c). But I afterwards remarked that no constancy 



prevailed in this, for I met with filaments, rarely it is true, 



in the cells of which the anterior ends of spores were turned 



to opposite sides (PI. IX. fig. 9), so that it could not be 



certainly determined in the unopened spores, which was the 



front and which the back. It need scarcely be mentioned, 



that accidental twisting of a filament was taken into account 



here. The end of the young plant, no matter whether it was 



the radical extremity or the growing summit, remained sticking 



in the burst coats (fig. 1 c, 11 c) long after the emergence of 



the other end, and the envelopes were not thrown completely off 



until a late period, and then either accidentally, or, as mostly 



occurred, by the young plant rising from the bottom of the 



water, where the germination took place. I never saw the 



liberated young plant become attached to anything by its 



radical extremity, and this corresponds to the ordinary floating 



condition of the Spirogyrce. But I cannot decide whether or not 



the SpirogyrcR become fixed to anything by their root-cell, at a 



later stage than that to which I was able to trace the young 



plants*. It is probable, however, that those Spirogyrce which 



are found adherent in their natural stations, use their root-cell 



as the organ of attachment. At the same time, the somewhat 



elongated basal cell, enlarged below into a shield- shaped root, 



described by Nageli as occurring in the Zygnemacese f , is 



certainly not the root-cell produced in the germination, but one 



of the ordinary filament-cells, enlarged into a short colourless 



expansion at one extremity. Whether the filament-cell thus 



altered is incapable of propagation, as Nageli asserts, I am 



inclined to doubt, since it is in any case certain that the true 



root -cell produced in germination is capable of transforming its 



contents into propagative cells in the shape of moving spores. 



* One of the largest of the young plants which I obtained iu a per- 

 fectly healthy condition was 2'6 mm. long. It was composed of thirteen 

 cells of tolerably equal length, excepting that the root-cell was longer ; so 

 that the length of these (subsequently dividing) cells of the young plant 

 equalled that of the larger, undivided (?) cells of older plants. 



t Gattungen einzellige Algen, p. 4. 



