. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . each oogonium there arenumerous oospheres or egg-cells, darkgreen in colour but with a con-spicuous receptive spot. Accordingto Klebahn (99) they may be eitheruninucleate or multinucleate. Theantherozoids enter the oogoniathrough minute lateral orifices inthe membrane (fig. 176 Bop). Afterfertilization the wall of the egg is atfirst very thin, but a second verru-cose wall arises underneath the firstone, and the conical verrucse of thismembran
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . each oogonium there arenumerous oospheres or egg-cells, darkgreen in colour but with a con-spicuous receptive spot. Accordingto Klebahn (99) they may be eitheruninucleate or multinucleate. Theantherozoids enter the oogoniathrough minute lateral orifices inthe membrane (fig. 176 Bop). Afterfertilization the wall of the egg is atfirst very thin, but a second verru-cose wall arises underneath the firstone, and the conical verrucse of thismembrane are connected by the first membrane isshed. The egg-cells become filledwith starch and oil, the latter havingdissolved in it a bright red ripe oospores rest for a longtime and can survive dry conditions,even for several years. On the germination of theoospore the chlorophyll becomesmore obvious and the contentsdivide into 2, 4 or 8 (according toMeyer, 06, always 4) parts, whichthen issue from a split in the oldwall as biciliated oval zoospores(fig. 176 D). These quickly undergoa transformation into spindle-shaped. Fig. 176. Sph&roplea annullna (Roth.) , part of coenocyte stained to show annularaggregates of small chloroplasts (ch), nuclei(n) and pyrenoids (py), x 440. B, parts oftwo ccenocytes with gametes and fertilizedeggs, x 440. a?f,autherozoid; o, oosphere; fo,fertilized egg; op, opening through wall ofccenocyte. C, part of coenocyte with ripeoospores (ro) showing the verrucose walls,x 440. D, one of the zoospores formed ongermination of the egg-cell, x 240. E and F,young plants formed from germinating zoo-spores, x 280. n, nucleus; py, pyrenoid.(B and D—F, after Cohn.) bodies, with much attenuated ex-tremities, and soon an annular appearance of the contents is plainly visible(fig. 176 F). The young plants grow rapidly in size and become muchelongated, acquiring numerous nuclei and pyrenoids, after which the firsttransverse wal
Size: 1122px × 2227px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishercambridgeengtheuni
