AUGUST, 1906.] THE ORCHID REVIEW. 227 
could not account for all the problems of heredity, and the question whether 
evolution was continuous or discontinuous could not be fully elucidated 
by Mendel’s researches. 
“Natural Hybrids of the Cattleya group ” was the title of the paper by 
Mr. R. A. Rolfe, who said that his object was to collect together the 
natural hybrids of this group, which had become rather numerous. A good 
many species grew more or less intermixed, and, as the insects upon which 
they largely depended for the fertilisation of the flowers did not confine 
their visits to any particular species, the opportunity for hybridisation 
arose. These hybrids were not often derived from the most closely allied 
species, which seldom grew together, in fact of forty-four recorded natural 
hybrids eleven were between Cattleya and Lelia— forming a sort of hybrid 
genus—and one between Cattleya and Brassavola, while of the remainder 
eight were Lelias and twenty-four Cattleyas. Among the latter were a 
good many combinations between two distinct sections of the genus. 
About eighteen of them had also been raised artificially. The earliest 
reference to the existence of a natural hybrid in the group was in 1856. 
He had arranged them chronologically and geographically, with an 
alphabetical list of references to descriptions and figures, for the literature 
of the subject was widely scattered. From a botanical standpoint, it was 
important that these curious intermediate forms should be taken at their 
true value, for they destroyed the natural limits of species, sections, and 
genera, and in practice it was found that, unless their real origin had been 
recognised from the outset, they had been classed as anomalous forms or 
varieties, or as distinct species, according to the amount of difference they 
presented from existing forms. A good many had been recognised as 
hybrids from the outset. In a few cases natural hybrids were common 
and very variable, and the question had arisen whether secondary bybrids 
might not occur, but this phase of the question was at present largely 
speculative. 
Prof. Pfitzer, of Heidelberg, read a paper on “ Hybridisation as a proof 
of natural affinity among Orchids,’ pointing out differences between 
classification based on floral and on vegetative characters, and the 
significance of genera which hybridised together. The natural arrange- 
ment of Orchids was not quite settled, but he held that genera which could 
be hybridised together were certainly nearly related. Among generic 
hybrids he mentioned the inexplicable case of Zygopetalum crossed with 
-Odontoglossum, in which the mother plant alone was reproduced. Mr. 
Rolfe remarked that the cause of this was not yet clear, and the experiment 
had been repeated more than once. It looked like a case of dominance 
absolute and complete, and if so the reverse cross should throw light on 
the question. He had tried to obtain the reverse cross, but without 
