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A BRYOLOGIST’S GLIMPSE INTO GEOLOGICAL HISTORY. 
John M. Holzinger. 
That even'the most modest efforts and observations may contribute 
important data to the illumination of profoundly scientific problems, is 
shown in the following letter from Dr. Emilio Levier, a physician in Flor- 
ence, Italy, and an enthusiastic bryologist. Dr. Levier makes so vivid a 
statement of the case and has so amiably permitted its use, that I feel justi- 
fied in giving it in full. 
“ Extraordinarily interesting to me was your discovery of the identity of 
the Cis-Caucasian Leskea crassiretis with the North American Fabroleskea 
Austini (See Bryologist, Sept. 1903). If I had known of this earlier I could 
have communicated to you two similar cases of widely separate localities 
which are very suggestive not only from the standpoint of phyto-geography 
but also of geological history. 
“The first case concerns, to be sure, not a moss, but a parasitic fungus 
which I collected in 1890, first at Trapezunt, later in western Trans-Cau- 
casia (Svanetia) on Rhododendron flavum, and which I sent for determina- 
tion to Prof. Magnus, of Berlin. Mr. Magnus believed at first he had a new 
species before him, entirely different from the European Exobasidium rhodo- 
dendri Cramer. However, he recognized very soon the complete identity of 
the fungus from the Caucasus with the North American Exobasidium dis - 
coideum Ellis, which grows in New Jersey on Rhododendron viscosum. In 
Europe there is at present no longer found any species of Rhododedron of 
the section Azalea maxim. {Pent anther a Don.). The Caucasian and North 
America Rhododendron are genuine, closely related Azaleas. Prof. Magnus 
then says this, in Sommier et Levier, Enumeratio Plant. Caucas.,p. 541: 
‘ These host plants, are relics from tertiary geological time, during which 
North America and Europe still constituted one common floral region. 
While the host plants in the two very distant areas which lay formerly 
within one common circle of distribution, were differentiated into two 
closely related species, the parasitic Exobasidium has maintained itself 
unchanged, at least in its external morphological characters. Exobasi- 
dium discoideum Ell. is a parasitic fungus which inhabited the parent 
forms of Rhododendron viscosum (L.) Torr. and of R. flavum Don. since the 
time when North America and Europe still formed one continuous floral 
region.’ 
“ In the two cases of Leskea and Exobasidium, Europe is completely 
overleaped and the two widely separate localties stand without connecting 
area: Caucasia-North America. (According to Reclus and many other 
geographers Cis-Caucasia to the south of the Manitch depression belongs to 
Asia and thus also the stations of Leskea grandiretis, but this in nowise 
alters the main point at issue.) 
“ Now we have a third case where a trace of an intermediate locality 
connecting the Caucasus with North America has been established by the 
discovery of a relic, no trace being left in all the rest of Europe. The case 
is that of a moss, Mnium ciliare. This moss grows and fruits abundantly 
