376 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



themselves to other filaments to form the network. Reproduc- 

 tion unknown. 



A genus of tropical algae, with beautifully symmetrical net- 

 like fronds, in which the filaments apparently anastomose, but 

 really are united by peculiar organs, "tenacula," formed on the 

 tips of the cells when they come in contact with other cells of 

 the fronds, or, in some species, of other fronds. The tenacula 

 are short cylindrical prolongations of the cell wall, ending in 

 dense short branches ; reminding one somewhat of the shape of 

 a sea-anemone. In the corresponding organs in Microdictyon 

 the attaching surface has a somewhat crenulate margin, but 

 does not develop branches. The primary cell of Struvca is at 

 first clavate, later spindle-shaped, and appears to attain its full 

 growth before the network is formed. There is some uncer- 

 tainty as to how the " articulations " of the network arise, but 

 it seems probable that it is by the deepening of the annular con- 

 strictions, not by true wall formation. 



KEY TO THE SPECIES OF STRUVEA. 



i. Stipe unbranched. i. S. anastomosans. 



i. Stipe branched. 2. 



2. Each branch of the stipe with a separate network. 



3. 5". ramosa. 

 2. One network only. 2. S. pulcherrima. 



i. S. ANASTOMOSANS (Harv.) Piccone, 1884, p. 20; S. deli- 

 catula Murray and Boodle, 1888, p. 281, PL XVI, figs. 6 and 8 ; 

 Vickers, 1908, p. 20, PI. XIX ; Cladophora anastomosans Harvey, 

 1855, p. 565, name only; 1859, PI. CI. Stipe smooth, simple, 

 slender, crowned with a subpyramidal network, 3-5 cm. long ; 

 filaments repeatedly pinnate, pinnae and pinnules opposite, 

 horizontally patent, more or less attached to each other. 

 Fig. 134. Guadeloupe, Jamaica. Australia, Canaries. 



This species shows a resemblance to the Pcllucida, section of 

 Cladophora; the union of the branches is only partial, and 

 varies much as to completeness. 



Var. CARACASANA Grunow in Murray and Boodle, 1888, p. 

 281 ; Vickers, 1908, p. 20, PI. XX. Frond regularly bipinnate ; 

 branches seldom united. Barbados. So. America. 



2. S. PULCHERRIMA (J. E. Gray) Murray and Boodle, 1888, 

 p. 281, PI. XVI, fig. 4. Stipe smooth, three-parted, crowned 

 with a single, cordate, three- ribbed network, 30X20 cm. ; fila- 



