198 JOURNAL OP THE [November, 



found numerous desmids, among them the Micrasterias denticu- 

 lata J also interesting infusorians, such as Stephanoceros Eich- 

 hornii. 



" The intense blueness of the Avaters of this lake has attracted 

 much scientific inquiry. Prof. Tyndall attributes it to the pres- 

 ence of mineral particles, probably glacier dust brought into the 

 lake by rivers, and of so extreme minuteness as not to settle 

 even when the water is allowed to stand a long time. Water 

 taken from a depth of twenty-five or more feet I found to be 

 almost cloudy when examined under the microscope, so heavily 

 charged was it with this dust." 



SILICIFIED WOOD FROM ARIZONA. 



Mr. M. M. Le Brun : " My specimens of silicified wood ex- 

 hibit the structure of the wood very perfectly in both transverse 

 and radial section. The lenticular markings characteristic of 

 the Coniferjc are preserved with special distinctness. 



" I have brought two photographs of the locality which fur- 

 nished this material. Of the many petrified tree-trunks shown 

 in them, one is deserving of particular mention on account of 

 its length and its situation. Tt is not less than one hundred and 

 fifty feet long, and it spans a wide caiion which has been formed 

 since the tree fell." 



Mr. Geo. F. Kunz : "On account of the great beauty and 

 variety of its coloring, this silicified, or agatized wood is begin- 

 ning to be used in jewelry. It is worthy to take the place of 

 Scotch agate and of blood-stone. With proper facilities for 

 transportation fully one thousand tons of the material would be- 

 come of commercial value for mosaic-work, table-tops, and other 

 ornamental purposes." 



BARBED AWNS OF ACHENIA OF BIDENS. 



The Rev. J. L. Zabriskie : " Whoever brushes against a plant 

 of the genus Bidens at its maturity has occasion to notice the 

 facility with which the seeds detach themselves from it and 

 cling to the clothing. Under the microscope each of the awns 

 crowning these achenia is seen to be furnished with, commonly, 

 three ranks of retrorse barbs which differ somewhat in character 

 in the different species. The barbs on the four awns of B. bi- 

 pifinafa, or Spanish Needles, are remarkable for length and 

 slenderness and for tlie acuteness of the angle which they make 



