. The algae. Algae. Fig. 137 Phyllophora hrodiaei. A, plant ( x ^). B, carpogonial branch ( x 250). Q transverse section of antheridial thallus ( x 450). D, nemathecia with tetraspores ( x 125). (A, original; B-D, after KyHn.) secondary tissue has been observed near the axils of branches or at the base of the frond. This is not surprising since the thaUi often last for many years and the successive increments are recognizable macroscopically. The plants are dioecious and the sex organs are borne in nemathecial cavities in small fertile leaflets that are at- tached to the main thallus. The carp
. The algae. Algae. Fig. 137 Phyllophora hrodiaei. A, plant ( x ^). B, carpogonial branch ( x 250). Q transverse section of antheridial thallus ( x 450). D, nemathecia with tetraspores ( x 125). (A, original; B-D, after KyHn.) secondary tissue has been observed near the axils of branches or at the base of the frond. This is not surprising since the thaUi often last for many years and the successive increments are recognizable macroscopically. The plants are dioecious and the sex organs are borne in nemathecial cavities in small fertile leaflets that are at- tached to the main thallus. The carpogonial leaflets, which are sessile or shortly stalked, arise laterally from the stipitate part of the main blade. Only one cystocarp is produced from each carpo- gonial nemathecium. In P. memhranifolia the carpogonial branch is three-celled and after fertihzation gonimoblast filaments are formed which ramify in the tissues, finally producing pedicellate or sessile cystocarps. In P. hrodiaei spermatia appear to be fimction- less and the carpogonium fuses directly with the auxiliary cell and the carposporic generation is omitted. This must be regarded as a reduction phenomenon in so far as the usual rhodophycean life cycle is concerned. The tetraspores-are borne in moniliform chains packed into wart-like excrescences or nemathecia which are borne on the female sexual plant. In P. hrodiaei the absence of carpo- spores led earUer investigators to regard the nemathecia as belong- ing to a parasitic plant, which in this case was given the name of Actinococcus suhcutaneus, but it has since been shown that we are really deahng with a parasitic diploid generation. Phyllophoraceae: Ahnfeldtia (after N. O. Ahnfeldt). Figs. 138, 139 The wiry and horny multiaxial thallus arises from a prostrate disc and is a perennial with secondary thickening. This results from 244. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability -
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Keywords: ., bo, bookcentury1900, bookcollectionbiodiversity, booksubjectalgae
