. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . divisions. The branches are felted together andtheir coherence is increased by small rhizoids (tenacula) growing out hereand there and firmly attaching themselves to neighbouring filaments. In all the Siphonocladeaa there are numerous small plate-like polygonalchloroplasts, many of which contain a central pyrenoid. Very often, but notalways, the chloroplasts are connected by fine prolongations from theircorners, so that in each coenocyte ther
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . divisions. The branches are felted together andtheir coherence is increased by small rhizoids (tenacula) growing out hereand there and firmly attaching themselves to neighbouring filaments. In all the Siphonocladeaa there are numerous small plate-like polygonalchloroplasts, many of which contain a central pyrenoid. Very often, but notalways, the chloroplasts are connected by fine prolongations from theircorners, so that in each coenocyte there is apparently a net-like chloroplast 256 Siphoiiocladiales with many pyrenoids. Internal to the chloroplasts there are numerous andvery evenly distributed nuclei. Starch-grains are also present, but they aremore particularly accumulated in the rhizoids. Zoogonidia may arise in any of the branch-segments, the zoogonidangiumconsisting of the original ccenocyte of the mother-branch and the branchgrown out from it but not yet cut off by a wall. The zoogonidia escape throughseveral orifices which are slightly protuberant, and they germinate Fig. 165. Struvea anastomosans (Harv.) Piccone. a and It, extremities of young stalks showingdevelopment of the frond. c, more advanced stage, d, single plant isolated from a tuft,showing the branched stalk with rhizoids. e, part of frond showing how the branchesare mutually attached by means of tenacula. /, chromatophores with pyrenoids. a—d,x about 6 ; e, x 20 ; /, x 250 (after Borgesen). Most of the Siphonocladese are tropical and subtropical ; they have a preference forsheltered localities and moderately deep water, although they do occur in less abundancein shallow water. Siphonocladus tropicus (Crouan) J. Ag. is often epiphytic on otheralgae, or, as in Ernodesmis verticillata (Kiitz.) Borges., it is not infrequently found in Boodlese 257 clumps. Struvea elegans Borges. occurs in deep water down to 40metres, aud may beco
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