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Howe: PHYCOLOGICAL STUDIES 515 
PLATE 26. Halimeda discoidea 
Photograph of a formalin-preserved specimen from Caesar’s Creek, Florida (xo. 
2964, 31 Mr 1904), natural size. 
PLATE 27 
1. Halimeda tridens. pada of a Setar NIE fertile specimen from 
Tallaboa, Porto Rico (#0. 4424, 22 Mr 1906), natural size. 
2-4. Halimeda Tuna. Hcesark a formalin- Sieeed fertile specimens from 
Culebra Island, Porto Rico (#0. 4207, 3 Mr 1906), natural size. 
PLATE 28 
1 and 2. Halimeda Tuna 
d 2. Spor. pacer: of apparently lateral origin from the central filaments 
and formed without fusion ; these were from the flattened face of a segment. 
e figures are dine from formalin-preserved material of our xo. g20z (Culebra 
io: ies Rico) ; the magnification is 24 diameters. 
3-7. Halimeda tridens 
3. A cluster of three sporangiophores from the margin of a segment; each is a 
continuation of a filament of the central strand coherent with the adjacent filaments 
near the point of emergence and anastomosing with th 
4. A sporangiophore from the flattened face oe a ‘saa: this is a direct con- 
tinuation of a utricle (distal series) of the subcortical layer. 
5. Base of peline so of origin similar to that shown in Figure 4. 
6 and 7. Bases of sporangiophores from the flattened faces of segmen h 
are direct ci aniee of the peripheral utricles; in Figure 6 the ad forks 
at the base, perhaps abortive 
Figures 3-7 are drawn froin formalin-preserved material of our no. gg24 (Talla- 
boa, Porto Rico) ; all are magnified 24 diameters. 
8-26. Avrainvillea nigricans 
8. Portion of surface of the flabellum, with exserted sporangia. 
“3 oung sporangia in various stages of development. Near the middle of the 
Stipe in Figure 13 is indicated the position of the mucous or callose plug. 
ag A sporangium which has aborted and resumed vegetative growth. 
. A nearly mature sporangium; the figure shows the mucous plug n 
base of the stipe and the usual relation of the sporangiophore to the seeds 
filaments, 
16. A young sporangium paired with an old and empty one. 
17. A sporangium with spores nearly forme 
18. A pair of empty and shriveled sporangia, . showing the wide erose or lacerate 
Opening at the apex of each and the mucous or callose thickening at the base of the 
Sporangiophore. 
9. A spore adhering to #7 mouth of an empty sporangium, where it has begun 
its extra- sporangial developm 
20. A hea septs Se ce ” left by the decay of an old sporangiophore. 
au. A € sporangium with four spores, A collection of granules at the apex 
Seems to indicave the area of the future rupture of the sporangium-wall. 
