Journal Number 103
May 2007

THE COLUMN

Petalochilus calyciformis (?)
By Eric Scanlen

Kevin Matthews has apparently rediscovered Petalochilus calyciformis as you can see in his Fig. 28 but the flower had not fully opened when he took this photo on 18 Dec 2006. A day or two later a frontal storm wrecked it and there were no more to be found in the vicinity.

This Kaitaia orchid may well be the one discovered by Henry Blencowe Matthews (Blen) who described the buds enthusiastically to T.F. Cheeseman on 14 Oct 1912 as, "...one variety of C. minor (Caladenia aff. chlorostyla) when in bud, looks precisely like the new find. ... the buds are very much larger, a greenish yellowish brown colour and more curved ...".

Cheeseman, the top New Zealand botanist of the time, regarded this orchid genus with its ordinary petal instead of a fancy labellum, as a "freak" and caused Blen's "sod to fall back in the furrow all the way along" as he replied. This is a well recorded historical incident which you can read about in Matthews and Son on orchids [1].

Australian taxonomist, Dr. R.S. Rogers, to whom Blen eventually sent specimens, had no qualms about describing this and another of Blen's, as a new genus, Petalochilus [2] and accompanied the description of P. calyciformis with the diagram in Fig. Below.

Notice the, "linear appendage with sigmoid flexure, furnished with a little cup at the apex, erect in
front of the column." as Rogers described it. This is thought to be the complex bulge ( Fig. 28 )
yet to separate from the column as the flower opens. Kevin assures us, there is no fancy labellum.

Other features of Rogers' description for leaf, bracts and ovary, fit the specimen well and his, "Segments of the perianth ... pubescent-glandular on the outside" is quite apt.

R.S. Rogers' drawing of Petalochilus calyciformis made from specimens sent by H.B. Matthews:
1. Column from side showing appendage.
2. Front view of flower (the artist has represented the labellum too long).
3. Column from the front showing appendage.

The similarity with Caladenia aff chlorostyla makes one suspect that this is a mutant form which
does seem to have survived for at least 100 years. Most new species arise from mutations so
Blen's 1912 colonies which were clearly seed dispersed thus viable, gave no obvious reason to
deny P. calyciformis specific status.

Neither Blen nor Rogers mentioned the spathe (or sheathing bract as Colenso described it for Nematoceras hypogaeum) at the base of the peduncle.

This translucent shovel shaped affair ( Fig. 29 ) showed up at Kevin's farm on P. calyciformis(?) as long ago as 9 Sept 2006 and had Kevin and the Column guessing for the next three months waiting impatiently for the flower to open whilst the peduncle extended. Fig. 28 is as near as it got.

Bruce Irwin had less luck with his probable find of the other species, P. saccatus back on 29 Sept 1997 at Scott Point [Journal 65:14, Dec. 1997]. The bud had been bitten off by a grub but revealed itself under his dissecting microscope as you can see in his drawings in J65.

Several subsequent visits by field parties have found Blen's Caladenia "nitida rosea" at Bruce's site but no further sign of Petalochilus saccatus.

Blen's and Rogers' genus continue to tantalise us but put you money on it, Kevin's site will be
closely watched next year!