I don't know how much interest there might be among the group in the
topic of orchid breeding, but I ran across the article below, and
found it's explanation of the dominance of reed-stem Epidendrum
phenotype enlightening:


http://www.bulbnrose.com/Heredity/H_ORCHID.HTM

Nature vol 59, 1898

Curiosities of Orchid Breeding
C. C. Hurst

....

Generic Hybrids
Of the 500 primary hybrids on record, about 100 are generic hybrids,
i.e. the parents belonging to different genera. In this respect alone
these hybrids are interesting, though no doubt the systematic botanist
views them with mixed feelings. It is not so long since generic
hybrids were looked upon as anomalies, some of the older naturalists
even regarding them as impossible, and forthwith proceeded to beg the
whole question by classing those genera which are fertile with one
another as species of one. Orchid growers, at all events, have almost
ceased to regard generic hybrids with curiosity, familiarity with them
having bred a certain amount of indifference.

A list of the generic hybrids on record up to the end of 1897,
together with a diagram showing how twenty-six different genera have
been linked together by artificial hybridisation, has been prepared by
the writer and was published in the Journal of the Royal Horticultural
Society (vol. xxi., April 1898), and to which those interested in the
details of generic orchid hybrids may be referred.

Generally speaking, primary generic hybrids follow the rule of
specific hybrids in bearing the intermediate characters of their
parents, with a narrow range of variation.

But there are a few remarkable exceptions to this rule.

(1) Epiphronitis x Veitchii, a hybrid out of Sophronitis grandiflora
(Lindl.) by Epidendrum radicans (Pav.)

(2) Epi-Cattleya x matutina, a hybrid out of Cattleya Bowringiana
(Veitch) by Epidendrum radicans (Pav.)

(3) Epi-Laelia x radico-purpurata, a hybrid out of Laelia purpurata
(Lindl.) by Epidendrum radicans (Pav.)

(4) Epi-Laelia x Charlesworthii, a hybrid out of Laelia cinnabarina
(Lindl.) by Epidendrum radicans (Pav.)


These four generic hybrids are very curious indeed, inasmuch as all
agree in reproducing the generic characters only of the pollen parent
Epidendrum, without the slightest trace of the peculiar structure of
the seed-parents, Sophronitis, Cattleya and Laelia. Yet in minor
characters, in colour, form and size, the four hybrids distinctly
differ from one another and from their Epidendrum parent.

A close examination reveals the fact that these minor differences
correspond with the peculiar differences in the parentage, thus
showing that the crosses have really been effected: yet as the same
time it must be candidly admitted that did we not know the parentage,
we could never have determined it, so overwhelming is the influence of
the predominant partner Epidendrum radicans. It will, no doubt, be
observed that E. radicans is the pollen parent in each of the above
cases. Curiously enough, when this reed-like E. radicans is crossed
with the pseudo-bulbous E. vitellinum (Lindl.), (female), a similar
result is obtained, the offspring E. x radico-vitellinum being
scarcely distinguishable from the reed-like E. radicans. Again, when
the reed-like E. x O'Brienianum— itself a hybrid out of E. evictum
(Hook. f.) by E. radicans— is crossed with the pseudo-bulbous E.
vitellinum, (female), a similar result is obtained, the offspring
being reed-like in habit as in the pollen parent. Yet when the
reed-like E. radicans is crossed with other reed-like species of
Epidendrum, and again when the pseudobulbous species of Epidendrum are
crossed with species of Laelia, in every case normal hybrids are
produced intermediate between their parents.

Though we cannot pretend to unravel this tangled skein, yet, so far as
experiments have been made, it seems quite clear that (1) the species
of Cattleya, Laelia, Sophronitis, and the pseudo-bulbous species of
Epidendrum, when intercrossed, produce normal hybrids intermediate in
character.

(2) The same result is obtained with the reed-like species of
Epidendrum are united with one another.

(3) But when the reed-like species of Epidendrum are united with the
pseudo-bulbous species of Epidendrum, or with species of Cattleya,
Laelia and Sophronitis, abnormal hybrids are produced, having the
essential characters of the reed-like Epidendra. From these facts it
might easily be argued that a reed-like Epidendrum was the ancestor
not only of the pseudo-bulbous Epidendra, but also of the more highly
specialised genera Cattleya, Laelia and Sophronitis. In that case the
pseudo-bulbous Epidendra would form an interesting connecting link
between the lowly reed-like Epidendra and the gorgeous aristocratic
Cattleya and Laelia.

....