Identifier: algvolimyxophy1916west Title: Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ Year: 1916 (1910s) Authors: West, G. S. (George Stephen), 1876-1919 Subjects: Algae Publisher: Cambridge [Eng.] The University press Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: bly have been derived fromChloro-desmis : Codium Stackhouse, 1795—1801 ; Pseudocodium Weber van Bosse, 1895.In- 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 in Pseudocodium the medullary filaments are longitudinally arranged and the branches of thecortical layer are coherent, so that in a superficial view the cortex is hexagonally areolate. Codium occurs in both the Eastern and Western hemispheres, but Pseudocodium is known only in the temperate regions of the Eastern hemisphere. The plants are perennial, and in Western Europe reproduction takes place freely in the winter. Family Phyllosiphonacese. This family includes some interesting endophytic or endozootic Alg*which in most cases are partial parasites. The tnallus of Pliyllosiphon consists of a richly branched coenocyte(fig. 156 B), tL°. rather irregular tube-like ramifications of which traverse in

Text Appearing After Image: Fig. 156. Phyllosiphon arisari Kühn. A, leaf of Arisarum vulgare showing the diseased areas caused by the Phyllosiphon ; B, branches of the Alga in the leaf-stalk, ×68 ; C, portion of algal thallus with aplanospores, ×340 ; D, aplanospores, ×400. (From Wille, after Just.) every direction the intercellular spaces of the leaves and leaf-stalks of various members of the Aracea?. Owing to this intrusion and the destructive action of the invader, the leaves of the host soon display diseased area sfrom 0-5—1 cm. in diameter, which often coalesce at their margins to form larger patches (fig. 156 A). These patches are at first yellow owing to the secretion of orange-yellow oleaginous droplets in the cells of the host due to the stimulation of the parasite. When the leaf wilt;S theoleaginous droplets disappear and the filaments of Phyllosiphon, which are now packed with green aplanospores, cause the affected spots to appear strikingly green on the withered leaf (Maire, 08). There are numerous

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