. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . possibly have been derived fromChlorodesmis : (Jodium Stackhouse, 1795—1801 ; Pseudocodium Weber van Bosse, Codium the medullary filaments form an irregular plexus and the branchesw. A. 16 242 Siphonales (utricles) which form the cortical layer are contiguous but not adherent; whereas inPseudocodium the medullary filaments are longitudinally arranged and the branches of thecortical layer are coherent, so that in a superficial view the
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . possibly have been derived fromChlorodesmis : (Jodium Stackhouse, 1795—1801 ; Pseudocodium Weber van Bosse, Codium the medullary filaments form an irregular plexus and the branchesw. A. 16 242 Siphonales (utricles) which form the cortical layer are contiguous but not adherent; whereas inPseudocodium the medullary filaments are longitudinally arranged and the branches of thecortical layer are coherent, so that in a superficial view the cortex is hexagonally occurs in both the Eastern and Western hemispheres, but Pseudocodium is knownonly in the temperate regions of the Eastern hemisphere. The plants are perennial, andin Western Europe reproduction takes place freely in the winter. Family Phyllosiphonacese. This family includes some interesting endophytic or endozootic Alga?which in most cases are partial parasites. The thallus of Phyllosiphon consists of a richly branched coenocyte(fig. 156 B), the rather irregular tube-like ramifications of which traverse in. Fig. 156. Phyllosiphon Arisari Kiihn. A, leaf of Arisarnm vulgare showing the diseased areascaused by the Phyllosiphon; B, branches of the Alga in the leaf-stalk, x 68 ; C, portion ofalgal thallus with aplanospores, x 340 ; D, aplanospores, x 400. (From Wille, after Just.) every direction the intercellular spaces of the leaves and leaf-stalks ofvarious members of the Aracea?. Owing to this intrusion and the destructiveaction of the invader, the leaves of the host soon display diseased areasfrom 05—1 cm. in diameter, which often coalesce at their margins toform larger patches (fig. 156 A). These patches are at first yellow owingto the secretion of orange-yellow oleaginous droplets in the cells of thehost due to the stimulation of the parasite. When the leaf wilts theoleaginous droplets disappear and the filaments of Phyllosipho
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