FEBRUARY, 1916.] THE ORCHID REVIEW. 35 
generation to another in certain bodies called chromosomes, in the egg and 
sperm. 
‘4, That the factors are generally linked together in groups, each 
chromosome having a group of its own; that they are arranged along the 
chromosome in a linear series, but sometimes change places with each 
999 
other by ‘ crossing over. 
The difference between factors and characters will probably be noted by 
the hybridist as significant, and he may possibly enquire as to the precise 
composition of these never-changing factors; how they originate—this 
especially; and how many of them co-operate to produce the visible 
characters of a Cypripedium that he may be working with? The argument 
is crystallised thus: ‘Inherited differences in individuals . . . are due 
to differences in their germ plasms. It is convenient to think of these 
differences . . . as being due to the presence of certain hypothetical 
units, which are usually referred to as factors. The factor nowadays is 
the ultimate unit of Mendelian research.’ And we would add that it is as 
elusive as the will-o’-the-wisp. Their existence in the form indicated is 
pure hypothesis, and the admission that they are in some way controlled 
by the environment may be taken as an indication of their mutability, and 
a concession that will be welcomed by students of evolution. 
The issue of Horticulture for January 15th contains descriptions of ten 
new varieties of Cattleya Percivaliana that are offered for registration by 
Messrs. Lager & Hurrell, namely: Aurora, spectabilis, resplendens, Stanley 
Ranger, superba, grandiflora, gigantea, Expanse, atropurpurea, and Oreol. 
It is a Public Notice, under the Society of American Florists and Orna- 
mental Horticulturists’ Department of Plant Registration, and ‘any 
person objecting to the use of the proposed names or registration is 
requested to write to the Secretary at once. Failing to receive objection 
to the registration the same will be made three weeks from this date.” 
The object of such registration is a good one, but whether it secures 
the desired end is another matter. Numerous varieties of C. Percivaliana 
have been recorded in various ways, and it is doubtful whether all the new 
comers would stand the test of comparison. But such so-called varieties 
are often only individual variations, which have a trick of disappearing, so 
that if similar forms afterwards receive different names it does not matter 
much. The idea of keeping complete records of varieties seems impossible 
in practice. 
Speaking of the subject of registration reminds us that a curious 
