Spirogyra dubia

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SPIROGYRA DU3IA, Ktz. - Fresh-water Algae of the United States page
18» February 1872* (Smithsonian contribution to knowledge,
£41).

Sp. viridis In fructe dilute viridis; artioulls sterillbus cylindri-
ols diametro l£-2& plo longlorlbus; fasciis spiralibus 2-3, an-
gustissimis, nodosis, anfractibus laxis 1*2 (- 3-6); cytioder-
mate utroque fine nee protenso nee repllcato, nonnihil erasso;
Zygosporis polymorphis, aut subglobosis aut ovalibus, aut sub-
oylindriois, diametro aequalibus aut § plo longlorlbus; arti-
oulis fertilibus cylindricis, haud tumidis.

Diam.-Art. steril 15/7500" * .002; spor. 15/7500" - .002".

Syn.-Sp. dubia, KTJTZI1TG. Rabenhorst, Flora Europ. Algsrum, Seot.

III. p. 243.

Hab.-In stagnis, prope Philadelphia.

Green, in fruit light green; sterile joints cylindrical l£~2£r
times longer than broad; spiral filaments 2-3, very narrow,no-
dose, lax, turns 1-2; oytioderm neither infolded nor protruded
at the end rather thick; zygospores polymorphous, either sub-
globose, oval, or subcylindrioal, as broad as long to -f times
longer; fertile articles cylindrical, not enlarged.

REMARKS.-I have found this species growing in the ditches below the
city, fruiting abundantly in May. When in this condition it
forms masses of a dirty, lightish, yellowish-green. The spores
mostly fill pretty well the fertile oells. My specimens do
not agree completely with the descriptions given of the Euro-
pean. The two forms, however, completely overlap one another,
except in one character, namely, the shape of the sporangial
cell. I have never seen it swollen or at all tumid in Amerioan
specimens, whilst in the European it is said to be "modioe tu-
midis." This difference alone does not, however, seem to me
sufficient to characterize a new species. I have seen speci-
mens of this plant collected by Or. Lewis at Cobble Mountain.
They agree veil with the Philadelphia specimens, except in
attaining a little large size, .0021", a nd in the sterile
filaments having their walls very thick. The character of non-
inflation of sporangial oells is perfectly preserved.

Fig. 4, pi. 17, represents this species.

4ILA0EUPHIA.

Fig. 4. SPIROGYRA DU8IA.	¡¡|

NEW YOR1
BOTANICA
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