IV. PETALONEMA ALATUM IN MINNESOTA. 



Daisy S. Hone. 



History. — This alga was discovered first in West Scotland 

 by Captain Carmichael, about 1823-1828, and was first figured 

 and described by Dr. Greville as an Oscillatoria. It has since 

 been found in various places in Europe, both in the British Isles 

 and on the Continent. In 1849 Harvey found it growing on 

 dripping rocks under Biddle Stairs, Niagara Falls, in America. 

 It was found by the writer near Minneapolis, Minnesota, in Oc- 

 tober, 1901. 



Collection and preservation. — The Minnesota material was 

 collected from the gravel bed of a quiet stream, the outlet of an 

 old tank near the Government Dam works, Minneapolis, on 

 October 12, 1901. It formed a dark chestnut brown stratum. 

 A portion was preserved in a 5-per-cent. formaline solution and 

 the remainder dried for herbarium specimens. The dried ma- 

 terial when soaked regains its original form so that it is as good 

 for study as the preserved. However, the formaline material 

 was used in the work recorded in this paper. 



Methods. — A small portion of the pickled material was 

 washed in water and then mounted directly in glycerine jelly. 

 If the jelly be raised above the melting point the threads col- 

 lapse. All the drawings used in this paper were made from- a 

 single slide which has been thus preserved. 



Staining in toto was tried with several fluids, but without 

 valuable result. After washing the material in water for twenty- 

 four hours it was treated with dilute hydrochloric acid for twenty- 

 four hours and then various staining fluids tried. A dilute 

 solution of Kleinenberg's hasmatoxylin stained the sheath a 

 beautiful blue, leaving the trichome deep green. Aniline safra- 

 nine stained the trichome red without affecting the sheath. 

 Dahlia colored the trichome a deep blue and slightly affected 

 the sheath. Fuchsin acid stained the whole red. Iodine turned 

 the trichome brown. 



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