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



laxus Howe, 1904, p. 95, PI. VI, figs, i and 2. Fronds up to 

 10 cm. high, rather soft and flaccid, 10-13 mm. diam. ; whorls 

 distinct, not very close ; sporangia ellipsoid to pyriform-sub- 

 clavate, 500-1000X325-450 /A, lateral or occasionally terminal on 

 branches of the first to the fourth orders ; aplanospores ellipsoid, 

 50-70 /A diam., i*/, times as long, in a single layer on the inner 

 surface of the sporangium. Fig. 145. Fla., W. I. 



Var. OCCIDENTALS (Harv.) Howe 19053, p. 579; Dasydadns 

 occidcntalis Harvey, 1858, p. 38, PI. XLJ.B. Fronds shorter 

 and smaller, whorls more closely set, ramuli less branched ; 

 sporangia spherical or nearly so ; aplanospores more numerous, 

 nearly filling the sporangium. With the type. 



The form described as B. Ocrstedi is a plant of quiet brackish 

 waters ; the var. occidcntalis inhabits exposed shores, and quite 

 resembles Dasydadus ; like the latter, the plants stain paper 

 yellow, while plants of the type do not. 



Family 5. SPHAEROPLEACEAE. 



Frond an unattached, riionosiphonous, unbranched filament, 

 consisting of long, cylindrical, multinucleate cells, each with 

 many minute, disk-shaped chromatophores arranged in distinct 

 zones, and many pyrenoids ; sexual reproduction by antheridia 

 and oogonia, which may be formed in the same or in separate 

 filaments ; antheridia formed of vegetative cells, unchanged in 

 shape and size, the contents becoming orange colored, and 

 transformed into a large number of long-clavate or spindle- 

 shaped, biciliate spermatozoids, escaping through numerous 

 openings in the cell wall ; oogonium from a vegetative cell, un- 

 changed in shape or size, the contents transformed into numer- 

 ous spherical, uninucleate oospores, fertilized by sperm atozoids 

 entering the cell by numerous openings ; oospore after fertiliza- 

 tion brick-red, with three colorless membranes, the outer mem- 

 brane ample and with wavy folds ; germinating oospore produc- 

 ing 1-8 biciliate zoospores, which on germination are much 

 elongated, and ultimately form a filament like the normal, but 

 with pointed ends ; unfertilized oospores may sometimes ger- 

 minate parthenogenetically. 



A rather isolated family, represented by only one genus. 



SPHAEROPLEA Agardh, 1824, p. XXV. 

 Characters of the family. 



vS. ANNULINA (Roth) Agardh, 1824, p. 76; Wolle, 1887, p. 

 104, PI. CXXIII, figs. 1-5; P. B.-A., No. 317. Filaments 27- 

 72 /j. diam., cells 8-20 diam. long ; 20-30 zones of chromatophores 



