. Dansk botanisk arkiv. Plants; Plants -- Denmark. we find it quite destitute of trichoblasts (comp. Fig. 272); it is straight and its diameter increases rather quickly down- wards from the small apical cell, which is constantly divided by horizontal walls. Upwards the filaments are rather richly ramified on all sides. The branches issue without any connection with the tricho- blasts (Fig. 274). The distance between the trichoblasts or branches varies consider- ably, sometimes these issue from each joint, sometimes 1—3 segments are bare. The trichoblasts are richly developed in some specimens,
. Dansk botanisk arkiv. Plants; Plants -- Denmark. we find it quite destitute of trichoblasts (comp. Fig. 272); it is straight and its diameter increases rather quickly down- wards from the small apical cell, which is constantly divided by horizontal walls. Upwards the filaments are rather richly ramified on all sides. The branches issue without any connection with the tricho- blasts (Fig. 274). The distance between the trichoblasts or branches varies consider- ably, sometimes these issue from each joint, sometimes 1—3 segments are bare. The trichoblasts are richly developed in some specimens, more sparingly or not at all in others. The tetrasporangia (Fig. 275 6) are found in long rows at the ends of the filaments. These are mostly undivided, sometimes forked. The segments con- taining the tetrasporangia are spherically swollen, about 80/^ broad. The antheridial stands of the Polysiphonias are, as is well known, formed by the trichoblasts, and with regard to these or- gans the present Polysiphonia belongs to the group of species (e. g. atrorubescens, jadigiata, scopulorum etc.)*) in which the whole trichoblast is trans- formed, not having even a sterile end, as is for example the case in Polysiphonia urceolata**). They (Fig. 275 a) are cylindrical in shape, with an obtuse apex, about 400—500 /^ long and 100—110 /i broad. The pedicel bearing the antheridial stand consists of two cells, the short basal cell always found in the trichoblasts, and a longer cylindrical one. Fig. 276. Polysiphonia The cystocarps originate from the second 'jjg^jj^f ^jf^e cystoIar|t cell of the trichoblast, as is commonly the (About 70:1). Fig. 275. Polysiphonia ma- crocarpa Harv. a, filament with antheridial stand; b, upper end of tetrasporic filament ia, about 360:1; b, about 50:1).. *) Cfr. Thuret et Bornet, Etudes phycologiques, p. 86. **j Cfr. RosENviNGE, L. KoLDERUP, Sur les organes piliformes des Rho- domelacées (Overs, k. danske Vidensk. Selsk. Forhandl. 1903, p. 450, fig. 2)
Size: 1433px × 1743px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectio, bookdecade1910, booksubjectplants
