. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 367. Fig. 359. Eucheuma isiforme (Ag.) J. Ag. a, Part of the thallus with tetrasporangia. b, transverse section of a branchlet with tetrasporangia. (a, about I'/a:!; 6,70:1). The specimens found were often more than a foot long. The thallus is of a very cartilaginous consistency; it is terete and, at any rate in the young specimens, oppositely or verticillately ramified. Some of the branches grow out to main branches like the mother branch; most of them remain short as spiny branchlets. The sum
. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 367. Fig. 359. Eucheuma isiforme (Ag.) J. Ag. a, Part of the thallus with tetrasporangia. b, transverse section of a branchlet with tetrasporangia. (a, about I'/a:!; 6,70:1). The specimens found were often more than a foot long. The thallus is of a very cartilaginous consistency; it is terete and, at any rate in the young specimens, oppositely or verticillately ramified. Some of the branches grow out to main branches like the mother branch; most of them remain short as spiny branchlets. The summit of the thallus consists of several filaments densely packed together. A transverse section shows that the thallus in the middle has a small medullary tissue composed of slender, but thick-walled cells. This is surrounded by a thick parenchymatic tissue whose cells are roundish-polygonal with rather thick walls. These cells are largest innermost growing gradually smaller towards the periphery. It is surrounded by the epidermal layer composed of short radiating fila- ments forming 2—3 layers of small, oblong, densely placed cells. At the periphery a rather thick epidermis is present. A longitudinal section shows that the cells of the medulla are long, cylindrical. They are twisted between each other and now and then ramified. The cells of the parenchymatic tissue have nearly the same shape as when seen in transverse section. Specimens with tetrasporangia and cystocarps are found. Both kinds of organs of fructification occur in the spiny branchlets (Fig. 359 a), the tetrasporangia also in the main stems. The tetrasporangia occur scattered in the cortical layer (Fig. 359 h). This is rather much developed. The cell-threads which form it are longer and consist of more cells than in the vegetative plant. The tetrasporangia are formed as a side-branch from these Please note that these images are extracted from scanned page images that may have been digitally enhance
Size: 2302px × 1086px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectio, bookdecade1910, booksubjectplants
