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BULB: Evolution of Bulbous Iris

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: BULB: Evolution of Bulbous Iris
  • From: Ensata <Ensata@aol.com>
  • Date: Tue, 16 Dec 1997 08:17:50 -0700 (MST)

When I ran across W. R. Dykes the other day, I remembered someone asking about
the evolution of blubous irises.  W. R. said that I could quote to you from
his book, ;-) A HANDBOOK OF GARDEN IRISES, by W. R. Dykes, 1924.  pp 18-20. (2
pages long)

"Of rhizomatous Irises it seems therefore that the Beardless species or
Apogons represent the oldest types of Iris and that from them have developed
the Bearded Pogoniris and the crested Evansias.  More recently still the
comparatively small, local sections of the Oncocyclus and Regelias species
have been developed from the Pogoniris.

There remains the problem of the bulbous species.  What was their origin and
are they older or younger than the rhizomatous sections?  There are at least
three distinct bulbous sections, the Xiphions, the Reticulatas and the Junos,
each of which is confined to a comparatively small area.  The Xiphions are
only found in Spain and in its geological extension in northwest Aftrica, with
the two exceptions of I. xiphium, which has an outlying station near Beziers
on the south coast of France and of I. juncea, which grows or grew near Palma
in Sicily.  The Reticulatas are natives of the Caucasus, Asia Minor, Syria and
northern Mesopotamia and are confined to that district, with the single
exception of the imperfectly known I. kolpakowskyana from Turkestan, which by
reason of its crocus-like leaves may constitute a distinct section of the
genus.  The Junos are the most widely distributed of all the Bulbous sections
for they extend from the habitat of I. alata and I. palestina round the coasts
of the Mediterranean and in Sicily, through Asia Minor, Mesopotamia, Turkestan
and Afghanistan to the Salt Range and the neighbourhood of Rawal Pindi in the

Curiously enough we can in each of these three cases point to nonbulbous
species, natives of the same areas, which seem to show traces of relationship,
or of development along similar lines, to the local bulbous species.  Thus in
Spain, the home of the various Xiphion species, we find I. spuria.  The shape
of its flowers and those of I. xiphium is almost identical and both these
species share the characteristic that drops of nectar stand out on the short
funnel-shaped perianth tube, which lies between the base of the segments of
the flower and the top of the linear tube, though this phenomenon is not
common in other species.

In Palestine and Syria among the reticulatas grows the small group of Apogon
species, of which I. Grant Duffii is typical.  Seedlings of this species by
the end of their first season will be found to have formed what are
practically bulbs with netted coats similar to those from which I. reticulata
took its name.  It is only in later years that a short rhizome is formed of a
succession of rings, each representing the base of the bulblike apex which
develops as the result of each season's growth.

The character, which separates the Juno Irises from all other bulbous species,
is the formation at the end of the growing season of thick store roots, which
remain unbranched during the season of rest in summer.  The characteristic
rhizomatous Irises of Asia Minor and Turkestan, the centre of the area of the
Juno species, are the Oncocyclus and Regelia sections, which both form stout
roots before growth ceases in early summer.  These roots remain unbranched
during the summer drought and only send out lateral rootlets after the coming
of the autumn rains.  They are not so stout nor so fleshy as those of the Juno
Irises but they have the property of remaining dormant for an equally long

The fact that the three bulbous sections are each confined to comparatively
limited areas seems to show that they are relatively late developments in the
history of the genus, but it does not seem possible to trace or even to
suggest the steps by which they have developed."         W. R. Dykes, 1924.

reprinted by John Coble at Ensata@aol.com

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