1884.] 



MICROSCOPICAL JOURNAL. 



subject, and considering the fact that 

 Mr. Berkeley is one of the leading 

 cryptogamist of Europe, his prompt 

 reply to my letter and the interest he 

 manifests in the subject is pleasing. 

 Mr. Berkeley states in reply that no 

 one has seen the perithecium of Oidi- 

 um in Europe, and further that he is 

 not aware that any one has seen the 

 perithecium as discovered by me on 

 the foreign vines of this country. Dr. 

 Taylor stated that he deemed it highly 

 pi'obable that the Oidium spores of 

 the native American vines had been 

 wafted to England from this country, 

 and were the real parent stock of Oidi- 

 um Tuckeri^ but he thinks that the 

 climatic conditions of Europe are un- 

 favorable to the development of its 

 higher form of fruit. He further 

 thinks it probable that the Oidium 

 he has discovered on the foreign vines 

 cultivated under glass in this country 

 are also of American origin and give 

 rise to l/ncinula spiralis — Berk, and 

 Curtis. If this view is correct, the 

 perithecia he has discovered on the 

 foreign vines represent in reality the 

 perithecia of Oidium T'uckej-i of this 

 country and of Europe. 



Dr. Taylor read the following letter 

 published in the Gardeners' Chroni- 

 cle from the pen of that great Apostle 

 of Cryptogamic literature. Miles Jo- 

 seph Berkeley, of England, relating 

 to the subject : — 



"The following very interesting 

 communication has been received 

 from Dr. Taylor, of the Department 

 of Agriculture, Washington, dated 

 October 28th : — ' This summer and 

 at this moment 100 foreign grape- 

 vines of 100 varieties are, so to say, 

 covered with the perithecia of an ery- 

 siphoid fungus of which I enclose spe- 

 cimens. I am fully aware that many 

 of the American varieties and some 

 of the species have the form Unci- 

 nula on them, but I am not aware 

 that any one has ever found any form, 

 subgenus, or species of this character 

 on the foreign grape-vines. You are, 

 I suppose, aware that in North Amer- 

 ica the foreign grape-vine is grow^n 



wholly under glass sti'uctures, Cali- 

 fornia excepted. The Oidiui7i Tuck- 

 eri is quite common on the foreign 

 vine. Within twelve years our for- 

 eign vines \vere aftected alike. I 

 I have watched each vear since 1S71, 

 but no perithecia were seen.' On ex- 

 amination of the specimens we find 

 the Uncinula^ as far as we can see, 

 to be identical with U. spiralis^ 

 Berk, and Curtis, having the same 

 long appendages, the tips of which 

 are distinctly spiral tips and not 

 merely hooked. This species was 

 sent to us by Mr. Curtis on leaves of 



Vitis labrusca. As far as we are 

 aware, like Dr. Taylor, no perithe- 

 cium has ever been developed on Eu- 

 ropean vines on which the Oidium 

 is so common and destructive. Pyc- 

 nidia have been found by Amici, but 

 no perithecia. It is, therefore, certain- 

 ly curious that perithecia should have 

 developed in America under glass, 

 and still more so that it should be a 

 specimen vv^hich occurs on the ^vell- 

 known Vitis labrusca. As that Un- 

 cinula is not known in Europe we 

 cannot suppose that it arises from the 

 historical Oiditim Tuckeri. With 

 the vine leaves there ^vas a leaf of 

 some American Vitis thickly clothed 

 with Capnodium elongation , Berk, 

 and Desm. It should be mentioned 

 that I found on the same leaf with the 



Uncinula a single perithecium, in an 

 imperfect state, of some Phyllacti- 

 niay 



Testing a Microscope. 



A few pi'actical hints about exam- 

 ining a new stand to find out its de- 

 fects may be of service, not only to 

 novices in the work, but to many 

 who have had experience in the use 

 of the instrument. It is not intended 

 to go thoroughly into the subject, but 

 only to allude to several details con- 

 cerning which it might puzzle some 

 pei"sons to decide. 



To test the centering of object- 

 ives. — The best way to do this is to 

 put a small object in the field, such as 



