lxxxvii 



to five feet in diameter were growing over the walls, ditches, and 

 inner area, and the whole surface was covered with a dense growth 

 of luxuriant bushes, vines, and trees. The ridges had evidently 

 been originally much higher, and the ditches deeper. The hill 

 faced the eastern edge of the Petite Osage Plains. On the 

 neighboring fields, human bones, spear heads, and remnants of 

 pottery, had been plowed up, and he had, himself, picked up 

 arrow-heads and spear-heads of flint in the same neighborhood. 



Dr. W. M. McPheeters presented specimens of petrified wood 

 of the stumps of trees found thirty miles northwest of Pike's Peak, 

 and a quantity of ores and fossils brought from Colorado Territory 

 by the Rev. Dr. Forman. 



Dr. McPheeters doubted the correctness of the theoiy of the 

 formation of such petrifactions of wood, by the substitution of 

 mineral substance in place of the decayed tissues. He thought 

 that an incrustation would be formed in such manner as to pre- 

 vent decay, and that some other theory must be resorted to for an 

 explanation of the phenomenon. 



Dr. Engelmann accounted for it by supposing a submergence 

 and a subsequent upheaval of the land, many such trees showing 

 evidence of having been submerged. 



Dr. Engelmann exhibited a plant of the genus Yucca, familiarly 

 known as Adam's needle and Spanish bayonet. He had dis- 

 covered the mode of its fertilization, and gave an abstract of a 

 paper on the subject which he desired to present to the Academy. 

 The paper was referred to the Committee on Publication. 



Novembei- 18, 1872. 



Vice-President Albert Todd in the chair. 



Seventeen members present. 



Dr. Engelmann said he wished to make some statements with 

 reference to the fossil-wood presented to the Society at its last 

 meeting. He had submitted it to several tests, and had found it 

 perfectly fire-proof, and chemical tests pioved the fibres to be 

 silex. He would further state that some of those present 

 thought the wood could not be petrified as some of it was rotten, 



