FAMILY I. BEGGIATOACEAE 841 



Trichomes 2 to 3 microns in diameter. fide had been generated by sulfate reduc- 

 Segments about 3 to 5 microns long; seg- tion. The genus 7'A2ospi/77?ops2;s may, there- 

 mentation difficult to observe without spe- fore, be more widespread than is generally 

 cial precautions. The spiral windings are believed, 

 regular. Source: Found in sulfur spring water at 



Comments: A very similar organism has Wekiwa Springs and Palm Springs, Florida, 



been observed at Pacific Grove, California, Habitat: Probably widely distributed in 



in a marine aquarium where hydrogen sul- water containing sulfur. 



Genus III. Thioploca Lauterborn, 1907. 

 (Ber. d. deut. botan. Ges., 25, 1907, 238.) 



Thi.o.plo'ca. Gr. noun thium sulfur; Gr. noun -plocc a twining, a braid or twist; M.L. 

 fem.n. Thioploca sulfur-braid or -twist. 



Trichomes are of Beggiatoa-VikQ appearance but occur in parallel or braided bundles en- 

 closed by a common, wide slime-sheath. The latter is frequently incrusted on the outside 

 with detritus. Within the sheath the individual trichomes are motile in the manner of Beg- 

 giatoa; the trichomes are segmented, the terminal segments often tapering. 



Closely resembles the genera Hydrocoleus and Microcolens among the Oscillatoriaceae. 



It is doubtful whether the members of the genus Thioploca are true colorless sulfur bac- 

 teria; most investigators of these forms have reported a greenish blue coloration of the 

 trichomes. Only the regular occurrence of sulfur droplets in trichomes taken from their natu- 

 ral habitat stamps the organisms as sulfur bacteria. In view of the close relationship of the 

 Beggiatoaceae to the blue-green Oscillatoriaceae, this is, however, a minor issue. 



Four species have been described to date. Three correspond, with respect to the indi- 

 vidual trichomes, to Beggiatoa arachnoidea, Beggiatoa alba and Beggiatoa leptomitijormis 

 respectively; the fourth appears to be a combination of the first and third of the above- 

 mentioned species of Beggiatoa in a common sheath. This occurrence of two distinct species 

 of Beggiatoa in a common sheath makes the genus a doubtful taxonomic entity. 



The type species is Thioploca schmidlei Lauterborn. 



Key to the species of genus Thioploca. 



I. Trichomes of a fairly uniform diameter occur in a common sheath. 



A. Diameter of trichomes is 5 to 9 mictons. 



1. Thioploca schmidlei. 



B. Diameter of trichomes is less than 5 microns. 



1. Diameter of trichomes is greater than 2 microns. 



2. Thioploca ingrica. 



2. Diameter of trichomes is less than 2 microns. 



3. Thioploca minima. 



II. Trichomes of greatly differing diameters occur in a common sheath. 



4. Thioploca mixta. 



1. Thioploca schmidlei Wislouch, 1912. sheath is variable. The trichomes are seg- 



(Ber. d. deut. bot. Ges., 30, 1912, 470.) mented, each segment measuring 5 to 8 



schmid'le.i. M.L. gen. noun schmidlei of microns in length. 



Schmidle. Source: Identified from various localities 



Individual trichomes, 5 to 9 microns in in Central Europe, 

 diameter, occur in a common, mucilaginous Habitat: So far reported only in fresh- 

 sheath, 50 to 160 microns in diameter. The water mud containing hydrogen sulfide and 

 number of trichomes embedded in one calcium carbonate. 



