1886.] 



MICROSCOPICAL JOURNAL. 



55 



ring 



ring, but in no case was such a 

 observed. 



The author allowed a microscope 

 to freeze to a block of ice, and to the 

 object-carrier a fine hair was at- 

 tached. ItAvas shrouded in thick mist, 

 and, although the temperature fell 

 to — io° C. , the minute drops of water 

 remained fluid, and were precipitated 

 upon the glass, and quickly evapo- 

 rated. Those drops that did not 

 evaporate in five or ten seconds re- 

 tained their form, and froze into solid 

 masses, without a trace of crystalline 

 structure to be seen. These particles, 

 however, were not examined for their 

 optical properties, which it would be 

 of interest to know. 



Pollen Tubes. — Mr. Charles R. 

 Barnes has studied the process of fer- 

 tilization in Companula Af/iericafia, 

 and published his results in an inter- 

 esting paper in the />'c/ff;/ /els'/ G«2-<'//£?. 

 He says : — 



' When the pollen tubes are emitted 

 on the stigma they sometimes pass 

 straight and sometimes after turning 

 upon themselves downwards between, 

 and not into, the bases of the papillae. 

 The conducting tissue runs close be- 

 neath the stigmatic surfaces. In this 

 tissue I have traced the tubes for sev- 

 eral millimeters. The pollen tubes 

 penetrate the strands of conducting 

 tissue and do not enter the canal of 

 the style. A short distance behind 

 the apex of the tubes cellulose plugs 

 are successively forined. These 

 plugs, which have sometimes con- 

 siderable length, are very prominent 

 objects in longitudinal sections of the 

 style or when the conducting tissue is 

 teased w^ith needles. The latter 

 method permits one to trace the tubes 

 for long distances. The pollen tubes 

 pass down the style and follow the 

 placentae. When they emerge from 

 a placenta they either enter the near- 

 est micropyle at once or pass further, 

 adhering very closely to the surface 

 of the placenta. 



' I have detected the pollen tubes 

 in a number of micropyles. The 



difficulty of tracing their further 

 course is greatly enhanced by the 

 opacity of the ovules and the conse- 

 quent necessity of adopting the sec- 

 tion method, as hereafter explained. 

 I have been fortunate enough to find 

 one specimen in which the pollen tube 

 had entered the micropyle and pene- 

 trated to the synergidae. 



' The main points established re- 

 garding the fertilization of Com- 

 panula Americana are these : — 



' The tapetal cells of the anther and 

 ovule are unusually large. 



' The pollen-spore possesses two 

 nuclei, one of which, the smaller, per- 

 sists and either with or without divis- 

 ion copulates with the female pro- 

 nucleus. 



' The pollen tube penetrates be- 

 tween the cells of the stigma and 

 passes down the conducting tissue and 

 not in the canal of the stvle. 



*■ There is the usual generative and 

 vegetative apparatus in the embryo- 

 sac' 



The methods of study are given in 

 considerable detail. 



Report of the Postal Club. — 

 The eleventh annual report of 

 the American Postal Microscopical 

 Club has been issued, with an ap- 

 pendix of extracts from the note- 

 books. It is particularly to the fea- 

 ture of the extracts from the note- 

 books that we would direct attention. 

 This portion of the report is of con- 

 siderable practical value as well as 

 interest, and it is likely to become an 

 important feature in subsequent re- 

 ports, if the prosperity of the Club 

 continues to increase as it has in the 

 past. Looking hastily through that 

 portion under Microscopy, we note 

 that Mr. Vorce recommends killing 

 insect eggs by placing them in car- 

 bolic acid. This may be a better 

 plan than a momentary dipping in 

 hot water. S. G. Shanks recom- 

 mends mounting starch in Farrant's 

 medium. In regard to wax cells, 

 Mr. Walmsley alludes to one which, 

 after passing through many circuits. 



