630 



SCIENCE 



[N. S. Vol. LIV. No. 1408. 



ential coloring that will make mycelium stand 

 out in contast to tlie tissue of the host have 

 been deseribed.'^ 



The writers, in an attempt to obtain a stain 

 * which would reduce the time required for the 

 examinations of a set of woods infected with 

 molds by producing satisfactory differentiation 

 both for visual examination and for photo- 

 micrography, have worked out the following 

 method. The results, although the work is 

 only in the preliminary stage, are so promising 

 that they are given here in order that others 

 .may avail themselves of the method if they 

 desire to do so. 



Since there is a difference in chemical com- 

 position between wood substance and chitin or 

 " fungous cellulose," the assumption was made 

 that the fungous mycelium might possess char- 

 acteristic mildly oxidizing or reducing proper- 

 ties. Then a solution of silver nitrate in dis- 

 tilled water was applied to thin sections of the 

 infected wood. These were allowed to stand 

 for periods of various lengths, overnight stain- 

 ing giving a very satisfactory result. The sec- 

 tions were then examined directly or dehy- 

 drated with alcohol, cleared with xylol, and 

 mounted in Canada balsam. Drying the bal- 

 sam mounts under weights in an oven over 

 night appeared, if anything, to improve the 

 stain secured. 



Both conifers and hardwoods were treated in 

 this way. The mycelium of several molds and 

 of two wood-destroying fungi has thus far been 

 stained. In all cases the mycelium was differ- 

 entiated by its blackish brown, purplish brown, 

 or orange color. The wood tissue presented, if 

 stained, a lighter shade of yellowish brown 

 against which the mycelium was readily visible, 

 often under relatively low magnifications. 



Silver nitrate solution also gave interesting 

 staining of the wood structures and cell con- 

 tents which will be discussed at some future 

 time. 



Gold chloride solution, and the " Berlin 

 Blue " stain, the latter as described by Dr. 

 Sophia Eckerson in her course in microchem- 



1 Sinnott, E. "W. and I. W. Bailey, Phytopath., 

 4 : 403, 1914. Vaughan, E. E., Ann. Mo. Bot. Gard., 

 5: 241, 1914 and others. 



istry,2 were also used with some success for the 

 same purposes as the silver nitrate. 



M. E. DiEMER, 



Chemist, 

 Eloisb Gerry, 

 Microscopist 

 Forest Products Laboratory, 

 U. S. Department op Agriculture, 

 Madison, Wisconsin 



sharks at san diego 



To the Editor of Science : It has occurred 

 to the writer that a very brief statement of 

 some experiences in collecting shark material 

 at San Diego, Cal., in 1920-21 might be of 

 value to persons interested in research prob- 

 lems in elasmobranch morphology and em- 

 bryology. Owing to the fact that the reduc- 

 tion plants in San Diego paid in 1920-21 a 

 price for sharks high enough to make it worth 

 while for the fishermen to bring in all such 

 material caught incidentally, and since nearly 

 all such material was brought to the fish- 

 market pier, at the latter place it was possible 

 in a very short time to collect a considerable 

 range of species. The writer obtained twenty- 

 six species of elasmobranchs at San Diego, 

 and the embryos of fourteen of them. No 

 other place along the Pacific coast, or prob- 

 ably on any other coast, offers such a wealth 

 of material and such easy access to it. It 

 was not uncommon to see fifteen species of 

 elasmobranchs at one time on the pier at San 

 Diego. jj. W. NoRRis 



Grinnell College 



municipal observatories 

 To the Editor of Science: In Science 

 for August 5, the Municipal Observatory at 

 Des Moines is " said to be the only mimicipal 

 observatory in the world." The Cincinnati 

 Observatory was incorporated in 1842, its 

 corner stone being laid in 1843 by John 

 Quincy Adams. Here Cleveland Abbe (di- 

 rector '68-'73) first issued daily weather re- 

 ports and laid the foundation of the U. S. 

 Weather Bureau. In 1872, the property was 

 transferred to the University of Cincinnati 

 (municipal) on condition that the city sup- 

 - Text-book now in preparation. 



