. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . iven a description of the attaching organs of a species whichmay be identified with Sp. adnata. The character of the attaching organsvaries much in the different species in which they have been found. Some-times they are simple rhizoidal outgrowths, but more often they are branched, 1 Although but rarely observed, branches have been known for a long time to occur inZygnema ericetorum ; they may consist of ten or even fifteen cells. In a small
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . iven a description of the attaching organs of a species whichmay be identified with Sp. adnata. The character of the attaching organsvaries much in the different species in which they have been found. Some-times they are simple rhizoidal outgrowths, but more often they are branched, 1 Although but rarely observed, branches have been known for a long time to occur inZygnema ericetorum ; they may consist of ten or even fifteen cells. In a small form of this species, described from the West Indies as Z. pachydermum (W. & G. S. W., 94), longitudinal septa of an incomplete character have beenobserved. - The only exception is Zygnema ericetorum. Consult p. 346. Zygnemacese 333 and they may be either lateral or terminal. In Spirogyra they may arise bya modificationof a conjugation-tube which has been protruded by a cell somedistance removed from those cells actually engaged in conjugation (West, 91;Borge, 94). The chloroplasts of those cells which have developed rhizoids. Fig. 209. A, young filament of Mougeotia sp. showing basal organ of attachment, x 100. B, Mougeotia capucina (Bory) Ag. showing the edge of the plate-like chloroplast, x 430. C, M. viridis (Kiitz.) Wittr., vegetative cells, x 445. D—H, Hass., x 445. /, (Hass.) Wittr., x 445. are often irregular and they frequently degenerate. In Spirogyra the nucleusmay also disappear, this taking place as a rule before the degeneration of thechloroplasts begins. 334 Conjugate In some instances the rhizoids may be formed as a result of the stimulus of contact,as in the profusely branched haptera described by Delf (13) in an attached Spirogyra,but in other cases, such as the replacement of a conjugation-tube by a branched rhizoid, thestimulus is obviously of another kind. Fragmentation of the filaments is of frequent occurre
Size: 1287px × 1940px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishercambridgeengtheuni
