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 //., lateral or occasionally terminal on 

 branches of t&e first to the fourth orders ; aplanospores ellipsoid, 

 50-70 /u, diam* , \y 2 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; Dasydadus 

 occidentalis Harvey, 1858, p. 38, Pi. XLJ.B. PYonds 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. occidentalis inhabits exposed shores, and quite 

 resembles Dasydadus ; like the latter, the plants stain paper 

 yellow, while plants of the type do not. 



Family 5. SPHAEROPL,EACEAE. 



Frond an unattached, monosiphonous, 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 spermatozoids 

 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. 



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

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

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



