PS-The Hoyan
Vol. 7, #3
JANUARY 2009
Pterostelma Section Hoyas
Anyone
who has ever done any Hoya research is constantly pressured by amateur growers
to tell them all about Sections. The
result is that some of us succumb to the pressure and end up with egg on our
faces. Degreed taxonomists appear to be
solidly against dividing hoyas into sections and with good reason. I merely suggested some sectional divisions
and have regretted it ever since because all I got was a lot of criticism and
constant badgering (some of it deserved).
It seems it will
never stop. So, if you
ever get the idea of writing me and asking me about sections, don’t expect a
reply.
HOWEVER ---- There is one “section” that I’d like to talk about
some more. That is the Pterostelma
(Wight) Hook. f. Section, which is typified by Hoya acuminata Benth. ex. Hook. f.
J. D. Hooker published this species in 1883, in Flora
of British India, vol. 4, page 53.
On this same page, he created the “Section
Pterostelma..”
Hoya acuminata was
the only hoya he included in this section; This publication was entirely in
English (the Code did not require Latin until the mid-1930s). J. D. Hooker’s publication is as
follows:
“SECT. H. Pterostelma. Corolla
reflexed, lobes longer than broad. Column sessile, obconic; coronal processes laterally
compressed, semi-cordate, 2-winged, with an erect subalate pointing the inner
angle. Plocostemma, Bl.
2. H. acuminata, Benth. in
Quite glabrous. Stem stout, 1-2 ft., subscandent and
pendulous. Leaves 3 - 4 by 1 - 1½ in.,
elliptic-lanceolate, nerves obscure; petiole ¼ - ½ in. Umbels terminal and Axillary, few-fld.; peduncles ½ in., pedicels
1 in. Sepals
linear-oblong, obtuse, ciliolate. Corolla-lobes 1 in.,
glabrous, tube puberulous within.
As
noted in the above publication, J. D. Hooker recognized Wight’s 1834
publication of the
Genus Pterostelma acuminatum * which was typified by Wallich’s Cat.
8170*2
Note,
also, that J. D. Hooker, the author of the Pterostelma Section placed the Genus
Plocostemma
into synonymy. I am sure that he did that because he knew that the Genus
Plocostemma was not published until 15 years after Wight’s publication
of the Genus Pterostelma and its type, Hoya lasiantha
is almost identical, in the features that count,
to Pterostelma
acuminata. The coronas are
extremely similar as are the corollas except for the wooly area at the base of
the coronas.
*Although Hooker f. spelled it acuminatum, Wight spelled
it acuminata
in his publication.
*2 Wight cited
Wall. Asclep. #129. This is the same as Wall. Cat. 8170. The specimen bears both numbers. All of
Wallich’s specimens appear to have been given two numbers.
………………………..
Here
is a translation Wight’s description of the Pterostelma Genus and it
type, Pterostelma acuminata Wight:
“VII PTEROSTELMA,
Wight. Calyx 5-parted. Corolla
rotate, 5-lobed.
To the above, Wight added, in English: “This genus is allied to Hoya both in habit and in
the structure of the flowers, differing principally in having foliaceous in
place of fleshy crown-leaves, and in the dorsal not lateral attachment of the
pollen masses to the corpuscle.
1.
P. acuminata (Wight). – Wall.! Asclep. N. 129 (absque nominee)* --In Silhet;
Wallich.
My
specimens do not possess a perfect umbel. –(R. W.)
* = Without a name.
……………………….
E-mail critic #1: “You are wrong about this and Hoya
lasiantha being Pterostelmas because Wight said that
the corollas are rotate.”
My reply: So he did, but he also said
that he did not possess a perfect umbel.
I was unable to find a flower picture on the Wallich
specimen but the above picture of a single flower on the Hooker f. type shows a
rotate flower. This flower is rotate due
to stage of development at the time it was pressed and dried.
You need to be aware that when an author publishes a
species name based on a pressed and dried herbarium specimen, he often has only
about 2 feet of plant
stalks with its attached leaves and flowers.
Sometimes the leaves are detached and in a pasted on envelope, as are
the flowers. When the flowers are
present they are often flattened and they are sometimes in various stages of
maturity. All the hoyas I’ve observed (n
more than 50 years of growing them) close their flowers before falling
off. Even those with reflexed flowers
don’t open up completely reflexed. They
open in stages and when their time is up they reverse the order and close in
stages. Whatever stage
a flower was in when the specimen was mounted and pressed is the stage the
author of this type of specimen will see and describe. If a full umbel (or more
than one umbel) is present, the author is likely to see flowers in all stages
of maturity but if, as Wight said, there is not a perfect umbel present, there
is no way the author can be sure is the flowers are rotate, campanulate,
recurved, reflexed or revolute. J. D.
Hooker had seen the Wallich specimen and had collected material from the same
area so his specimen gives us a better picture.
I
made my own picture of a specimen I found at Arnold Arboretum (
The above is a slightly reduced portion of the holotype
specimen of Hoya myanmarica P. T.
Li.
It is F. Kingdon-Ward #21190. The sketch in the bottom right corner is a sketch I made of
one of its flowers while looking at it through a microscope. I was able to do that when I had the Arnold
Arboretum (Harvard) collection on loan in the mid-1980s.
Hoya myanmarica P. T. Li is a synonym for Hoya
acuminata (Wight) Benth. ex. Hook. f.
This makes Hoya acuminata the correct name
because it came first. Hoya
acuminata was published in 1883; Hoya myanmarica was published in
1994.
On
the lower half of the Hoya myanmarica holotype specimen,
Kingdon-Ward wrote some descriptive words that do not appear in P. T. Li’s
description, nor in J. D. Hooker’s. Those words are, “An epiphytic shrub, the
flowering branches erect, eventually as they grow longer, flopping and
hanging. Flowers snow white, the long
corolla lobes completely reflexed.” Note
that Wight was uncertain if this were a twining shrub or a decumbent
plant.
The
three specimens (Wight’s type; Hooker f.’s type and P. T. Li’s type)
remind me of Hoya javanica and
somewhat of Hoyas cumingiana and densifolia but what a great
difference its flowers are. These
flowers measure up to and sometimes more than two inches in diameter!
The following is the late Hon. Douglas H. Kent’s take
on the subject as noted in a manuscript he and I were working on at the time of
his death:
“Hoya acuminata (Wight) Benth. ex Hook. f., Fl. Brit.
Pterostelma acuminata Wight, Contr. Bot. Ind. 39 (1834). (Lectotype:
Cyrtoceras acuminatum Regel, Cat. Pl. Hort. Aksakov. 46 (1860), nom. nud. Hoya griffithiana Decne. ex. Hook. f. (1883).
In Syn. Hoya myanmarica P. T. Li
1995).
Illustration: Hoyan
12(4): 96 1991).”
WHERE CAN ONE GET CUTTINGS OF PLANTS
OF THIS SPECIES? At the present time (January
2009) it is not yet in circulation, unless it is being distributed under a
different name. Hoya collectors appear to have been collecting in every known
habitat except
Hoya Book
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European price is 33
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