FAMILY III. CRENOTRICHACEAE 



273 



able variation in the diameter of the indi- 

 vidual trichomes, the base measuring 1.5 

 to 5.0 microns and the swollen tip measur- 

 ing 6.0 to 9.0 microns. Each trichome is sur- 

 rounded b}' a colorless sheath which later 

 may become rust-colored and heavily en- 

 crusted, especially at the base, with deposi- 

 tions of ferric hydroxide and, to a lesser 

 e.xtent, manganese oxides. The ensheathed 

 trichomes may reach a diameter of 12 mi- 

 srons or more. Cells within the trichomes 

 are usually about 1.5 times as long as they 

 are wide and are more or less rectangular in 

 shape. 



During reproduction the cells divide by 

 longitudinal and transverse fission into non- 

 motile conidia of two types: microconidia, 

 which are 1 to 2 microns in diameter, and 

 macroconidia, which measure about 5 

 microns in diameter; intermediate forms 

 may also occur. When the tip of the sheath 

 ruptures, the conidia are extruded; these 

 may attach themselves to some object and 

 grow into trichomes, or they may germinate 

 upon the exterior of the sheath from which 

 they were liberated, giving rise to new tri- 

 chomes attached to the surface of the older 

 one, thus simulating false branching. The 

 conidia often form a zoogloeal mass, but 

 only in the presence of dissolved iron. 



In addition to the above-mentioned types 

 of reproductive cells, Cohn (ibid., 120) ob- 

 served a third structure which he condi- 

 tionall}'^ alluded to as a spore. These cells 

 originate from the swollen terminal cell 

 which is usually ellipsoidal in shape and 

 sometimes as much as seven times as long 

 as it is wide (3.67 by 26.25 microns). The 

 protoplasm of this terminal cell becomes 

 finely granular and eventually emerges from 

 the sheath. From these cells, short, color- 

 less Oscillaria-like trichomes are produced 

 which contain no more than eight cylindri- 

 cal cells measuring 5 to 6 by 10 to 12 microns. 

 The trichomes have a characteristic, slow, 



gliding motion and are surrounded by a fine, 

 transparent membrane, but no sheath. 

 Subsequent authors, when describing this 

 species, have usually failed to mention this 

 third type of reproductive cell observed by 

 Cohn. 



Cultivation: Has not been grown on 

 artificial media in pure culture. Grows 

 readily in water containing organic matter 

 regardless of the iron content of the water. 



Related species: Cholodny believed 

 Clonothrix fusca to be identical with Creno- 

 thrix polyspora. However, Clonothrix ftisca 

 shows genuine false branching and produces 

 conidia by fission in only one plane so that 

 the trichomes taper toward the tip instead 

 of expanding (see Kolk, Amer. Jour. Bot., 

 25, 1938, 11, for a differentiation of these 

 two species). 



Comments: Zopf (Entwicklungsgesch. 

 Unters. (i. Crenoihrix polyspora, die Ursache 

 der Berliner Wasserkalamitat. Berlin, 1879, 

 2) regards Leptothrix kuehniana Rabenhorst 

 as identical with Crenothrix polyspora Cohn, 

 and there seems to be much evidence in 

 favor of considering the tw-o species as 

 identical. If Cohn's organism proves to be 

 identical with Rabenhorst's, then the spe- 

 cific epithet kuehniana has priority over 

 polyspora; however, until the relationship 

 of the two organisms has been clarified, the 

 name Crenothrix polyspora is retained here. 



Source: This organism is wide-spread in 

 water pipes, drain pipes and springs w^here 

 the water contains iron. It frequently fills 

 pipes under such circumstances and causes 

 a real nuisance. Found by Cohn in samples 

 of water from springs in the neighborhood 

 of Breslau, Germany. 



Habitat: Found in stagnant or running 

 waters containing organic matter and iron 

 salts. Harmless, but frequently becomes 

 bothersome in w^ater pipes and city water 

 supplies; grows as thick, brownish masses. 



Genus II. Phragmidiothrix Engler, 1883. 



(Vierter Ber. d. Commission z. wissensch. Unters. d. deutsch. Meere in 

 Kiel fiir 1877 bis 1881, I Abt., 1883, 187.) 



Phrag.mi'di.o.thrix. Gr. noun phragma fence; Gr. noun eidus form, shape; Gr. noun 

 thrix, trichis hair; M.L. fem.n. Phragmidiothrix fence-like hair. 

 Trichomes are articulated, unbranched and attached, the free ends being swollen. Sur- 



