146 proceedings: botanical society of WASHINGTON 



Defects in wood in relation to airplane construction: Lieut. J. S. BoycE. 

 Since airplane construction aims to secure the maximum strength with 

 the minimum weight, it is self-evident that wood with any defects 

 which weaken it appreciably must not be used for this purpose. 



One type of defect is the so-called advance rot, which is merely the 

 early stages of decay, the fungus mycelium having already invaded and 

 weakened the wood, but the only microscopical evidence of this condi- 

 tion is a slight discoloration of the wood. Advance rot is quite prev- 

 alent in the more important woods used in airplane construction, 

 among which are Sitka spruce (Picea sitckensis), Douglas fir {Pseudo- 

 tstiga taxifolia), yellow birch {Betida lutea), white oak (Otiercus alba), 

 and white ash (Fraxinus aniericana). Considerable skill is necessary 

 to separate stock with advance rot from that with harmless discolora- 

 tions resulting from chromogenic fungi or other causes. 



Very slight lightning wounds, known as "lightning rings," are serious 

 defects in airplane members, since there is a decided tendency for the 

 wood to separate easily along the annual rings in which such wounds 

 occur. 



In order to make such defects properly understood in their relative 

 importance, it will be necessary to disseminate information in simple 

 form concerning the structure, mechanical properties, and defects of 

 wood throughout the airplane industry. 



The 132nd regular meeting of the Society was held in the Assembly 

 Hall of the Carnegie Institution at 8 p.m., Wednesday, January 15, 

 1919. Thirty members and five guests were present. Mr. Clifford 

 H. Farr, of the Bureau of Plant Industry, was elected to membership. 

 The following papers were presented: 



The potash-containing marls of the eastern United States: R. H. True. 

 Greensand marls were first recognized in America in 1768 near Marl- 

 boro, New Jersey. After the Revolution their use as fertilizers de- 

 veloped rapidly, marl railroads having been built in the early thirties 

 to haul marl from the most valuable deposits to the surrounding farm- 

 ing country. In the early forties over a million tons were shipped by 

 rail in one year in this state alone. The digging of similar deposits 

 discovered in Virginia began about 1833 and ceased only when the Civil 

 War broke out. The war and the heavy demand on labor led to the 

 ready adoption of guano, ground bone, and other concentrated fer- 

 tilizers, and marling practically ceased. 



In 1824 Seybert found them to contain calcium carbonate, potassium^ 

 and other substances. Rogers and others claimed chief value for potas- 

 sium, Ruffin for the lime. With the present shortage of potassium 

 these marls furnish a useful source for a very great supply over a prac- 

 ticable hauling radius. Marl samples collected in New Jersey and in 

 Virginia when used in sand cultures yield sufficient available potassium 

 to support a normal growth when supplied at the rate of five or more 

 tons per acre. 



Germination of immature seeds: J. B. S. Norton. The consideration 

 of immature seed har\^ested under certain conditions in the case of 



