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



i. PHYLLOSIPHON Kiihn, 1878, p. 32. 



Parasitic in the leaves and stems of flowering plants ; ends of 

 the filaments and their branches without chlorophyll, lower 

 parts with chlorophyll, but with little indication of definite 

 chromatophores ; asexual reproduction by aplanospores, with 

 distinct parietal chromatophore, escaping by rupture of cell 

 wall. 



P. ARISARI Kiihn, 1878, p. 32; Just, 1882; p. i, PI. I; P. 

 B.-A., No. 1285. Filaments 25-35 P- diam., during spore form- 

 ation up to 60 /A diam.-, irregularly or dichotomously branched, 

 creeping between the cells in the parenchyma of the leaf or 

 petiole of the host plant ; forming larger or smaller yellowish 

 patches, up to several cm. diam., each patch formed of a single 

 individual ; aplanospores formed in great numbers, ovoid, about 

 5X2. 5 p.; development unknown. Fig. [57. N. H. Europe. 



In Europe this plant infests Arisarum vulgare ; here the 

 nearly allied Arisaema triphyllum. In spite of its abundant 

 chlorophyll it appears to be a true parasite, drawing its supplies 

 from the cells of the host plant, which it ultimately exhausts ; 

 but it does not penetrate the cells, nor are there any specialized 

 haustoria. 



2. OSTREOBIUM Bomet and Flahault, 1889, p. CL,XIII. 

 Fronds tubular, branched, with occasional swellings ; living 

 in the shells of mollusks ; reproduction unknown. 



O. QUEKETTII Bornet and Flahault, 1889, p. CIvXIII, PI. IX, 

 figs. 5-8. Fronds slender, in main divisions 4-5 /x diam., with 

 numerous lateral, divaricate branches, which by repeated 

 branching form a close network, the ultimate divisions about 

 2 /A diam. ; occasional irregular swellings in the filaments, 20-40 

 /u, diam. In old shells of oysters and other mollusks. Fig. 159. 

 Mass., Conn. J^urope. 



This species often grows in company with Gomontia polyrhiza, 

 from which it is easily distinguished by the continuous, not 

 cellular filaments ; the swellings would seem to indicate repro- 

 ductive organs of some sort, but nothing has been found in them 

 different from the contents of the more slender parts. 



Family 5. CAULERPACEAE. 



Frond tubular, multinucleate, unicellular, traversed by cross 

 strands of cellulose. Reproduction by division of the frond ; no 

 other method known. Containing only one genus. 



