Miscellaneous Intelligence. 445 



13. Microscopic Examination of Gun-Cotton; by Dr. Bacon, (Proc. 



Boston Soc. Nat. Hist., Feb., 1847, p. 195.) — Specimens of the cotton, 

 before and after preparation, were put up in Canada balsam on slips of 

 glass, and covered by very thin glass. When viewed by transmitted 

 light, with powers from 150 to 800, many of the fibres of the gun-cot- 

 ton appear thickened, but no other change can be perceived on com- 

 parison with the unprepared article. There is no appreciable differ- 

 ence in the transparency of the two. 



They were now examined in polarized light by means of the polar- 

 izing attachment to the microscope. When the polarizing and analy- 

 zing prisms are so arranged as to afford a dark field, the riband-like 

 fibres of the cotton before preparation are seen as luminous objects 

 upon a black ground, and are tinged with bright and varied colors. 

 They are thus proved to possess a strong polarizing power. The gun- 

 cotton, under the same circumstances, presents an entirely different 

 appearance. Its fibres are much less luminous, and have a nearly 

 uniform dull blue color. It is evident that the process of preparation 

 has so altered the structure of the fibres as to lessen very greatly their 

 action on polarized light. 



Gun-cotton prepared by Dr. Jackson by immersion for twelve and 

 for eighteen hours in the strongest acids, has not lost its polarizing 

 power in any appreciably greater degree than after an immersion of 

 three minutes only. This agrees with the results of other modes of 

 trial in indicating that the latter period is sufficient for the complete 

 preparation of the cotton, when the acids are of full strength. In all 

 the specimens there are some filaments so nearly destitute of polari- 

 zing power as to be scarcely visible on the black ground, but none 

 have been found entirely without action. When the polarizing and 

 analyzing prisms are in such a position as to give a bright field, a por- 

 tion of the fibres becomes tinged with a color approaching to orange, 

 while the remainder appear colorless as in ordinary light. 



14. On the Production of Vanilla in Europe, (Gardner's Travels 

 in the interior of Brazil, p. 296; Jameson's Jour., xlii, 382.)— In 

 marshy bushy places on this journey, I saw many plants of the Vanilla 

 planifolia, seldom bearing flowers, and more rarely producing fruit. 

 It has now been satisfactorily determined, that this is the species from 

 which the true vanilla of commerce is procured. In Mexico it is exten- 

 sively cultivated for the sake of its fruit, which it yields abundantly : 

 while the plants which have been introduced into the East Indies, and 

 the hothouses of Europe, though they have frequently produced flow- 

 ers, have very seldom perfected their fruit. Dr. Morren of Liege was 

 the first to study attentively the natural history of this plant, and to 

 prove experimentally that the fruit of the vanilla may be as freely 

 produced in our hothouses as it is in Mexico. He has discovered that 



from some peculiarities in the reproductive organs of this plant, anifi- 

 cial fecundation is required. In the year 1836, a plant in one of the 

 hothouses in the botanic garden at Liege produced fifty-four flowers, 

 which having been artificially fecundated, exhibited the same number 

 of pods, quite equal to those imported from Mexico ; and, in 1837, a 

 fresh crop of about a hundred pods was obtained upon another plant 

 by the same method. He attributes the fecundation of the plant in 



