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cp noob needs help distinguishing two petiolaris species... pics would help.

hello everyone,

was wondering if i could get some cleared air regarding this subject matter-- how does one distinguish D. petiolaris with D. diliatatopetiolaris? cpphotofinder doesnt really help much as there is either too many pictures to sift through or nothing, at least that i see. reading taxonomic differences leave me scratching my head. would definitely appreciate info from someone who possesses both of these species to give me a side by side comparison of the leaves, flowers, size, whatever...

much appreciated. cheers.
 
I've wondered this myself. I have both in my collection and they are about the same size and coloration. The only thing I have noticed is that petiolaris seems to get a little bigger. Sorry that wasn't much help maybe there's a difference in petiole length or something like that???
 
Download this file and key the characteristics out:
http://lrm.nt.gov.au/__data/assets/pdf_file/0020/122087/DROSERACEAE.pdf

One of the main keys used to be linear/near linear petioles (D. petiolaris) vs oblanceolate petioles (D. dilatatopetiolaris). However Kondo's original diagnosis appears to be incomplete as the petioles on D. dilatatopetiolaris are polymorphic and change from linear to oblanceolate with the age and flowering of the plant. It appears that many plants keyed out as D. petiolaris may actually be D. dilatatopetiolaris.

In Lowrie's paper New species in Drosera section Lasiocephala (Droseraceae) from tropical northern Australia (search for it online) his taxonomic key shows the significant characteristic if the petioles are linear on D. petiolaris are wooly hairs on the inflorescence (including scape). D. dilatatopetiolaris has simple branched hairs on the scape and wooly dendritic hairs on the sepals and pedicels.

So if the petioles are oblanceolate it is most likely D. dilatatopetiolaris (check for simple branched hairs on the scape). If the petioles are linear/near linear it is D. petiolaris if the scape has wooly hairs.
 
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@NaN: thanks. downloaded. though the pdf only seems to detail D. dilatatopetiolaris extensively, and not much is given about D. petiolaris, although that could be all that is necessary. darn dilatatopetiolaris being polymorphic. :cuss:

i also wish my plants flowered. they have not done anything like the sort since i got them, which could help distinguish between the species.

@mcmcnair: you say you have both? did you obtain them through a primary source or by trade? size could be a possibility for distinguishing species as well, as i hear petiolaris is the giant out of all other species.
 
my dilatatopetiolaris I got in a trade with Smitty and my petiolaris I ordered from a european vendor.
 
Here's de Candolle's original description from 1824:
dpetiolaris.jpg

not really worth translating from Latin

Lowrie cites these works in his papers:
http://www.environment.gov.au/biodiversity/abrs/publications/flora-of-australia/vol08.html
http://www.publish.csiro.au/paper/BRU9800209.htm

The book is out of print but you can find a used copy. A reprint of the journal article can be bought for $25
 
Dpetiolarisred040706RS.jpg

I never completely understood the delineation between the two. There were some plants that were obviously dilatatopetiolaris but Sean Spence felt strongly that the plant above also fell into this designation iirc. The conversations on CPUK are probably still available with a search... (or pm him for his thoughts).
 
  • #10
Looking at the first picture again with a few hours in-between I'd now say the petioles are linear/near linear. Ha ha, that's how it goes. There is no scale but I'd guess the petioles are 2mm-4mm in width. Without inflorescence using Lowrie's key this is the best I can do:

3 Leaves at anthesis densely covered with appressed hairs; petiole hidden by
the dense hairy covering .............................................................................................................. 4
3 Leaves at anthesis sparsely covered with appressed hairs; petiole visible
through the hairy covering........................................................................................................... 6


6 Lamina reniform, 15-20 mm wide .................................................................................. D. falconeri
6 Lamina orbicular, suborbicular or transversely broadly elliptic to very
broadly ovate, 2.5-7 mm wide ....................................................................................................... 7

7 Lamina transversely broadly elliptic to very broadly ovate, 5.5-7 mm
wide leaves appressed to the soil surface ................................................................ D. kenneallyi
7 Lamina orbicular or suborbicular, 2.5-3.5 mm wide; leaves of the
rosette more or less horizontal to the soil surface or erect to semi-erect ..................................... 8

8 Leaves of the rosette more or less horizontal to the soil surface.................................................. 9
8 Leaves of the rosette erect to semi-erect .................................................................................... 10
9 Inflorescence (including scape) 5-15 cm long ........................................................D. darwinensis
9 Inflorescence (including scape) 30-40 cm long........................................................ D. brevicornis

10 Petiole oblanceolate ................................................................................................................... 11
10 Petiole linear ............................................................................................................................... 12

11 Inflorescence (including scape) up to 18 cm long; pedicels
3-7 mm long ................................................................................................... D. dilatato-petiolaris
11 Inflorescence (including scape) up to 45 cm long; pedicels
1-2 mm long ........................................................................................................................D. fulva
12 Inflorescence (including scape) glabrous .............................................................. D. broomensis
12 Inflorescence (including scape) covered with woolly hairs ....................................... D. petiolaris


With the second plant, again without benefit of scale or inflorescence from Lowrie's Key:

3 Leaves at anthesis densely covered with appressed hairs; petiole hidden by
the dense hairy covering .............................................................................................................. 4

3 Leaves at anthesis sparsely covered with appressed hairs; petiole visible
through the hairy covering........................................................................................................... 6
4 Petiole oblanceolate, 2-4 mm wide ............................................................................... D. ordensis
4 Petiole linear or very narrowly oblanceolate, < 2 mm wide ........................................................... 5
5 Petiole linear, covered with dendritic hairs ..................................................................... D. lanata
5 Petiole very narrowly oblanceolate, covered with non-dendritic hairs..................... D. derbyensis

6 Lamina reniform, 15-20 mm wide .................................................................................. D. falconeri
6 Lamina orbicular, suborbicular or transversely broadly elliptic to very
broadly ovate, 2.5-7 mm wide ....................................................................................................... 7

7 Lamina transversely broadly elliptic to very broadly ovate, 5.5-7 mm
wide leaves appressed to the soil surface ................................................................ D. kenneallyi
7 Lamina orbicular or suborbicular, 2.5-3.5 mm wide; leaves of the
rosette more or less horizontal to the soil surface or erect to semi-erect ..................................... 8
8 Leaves of the rosette more or less horizontal to the soil surface.................................................. 9

8 Leaves of the rosette erect to semi-erect .................................................................................... 10
9 Inflorescence (including scape) 5-15 cm long ........................................................D. darwinensis
9 Inflorescence (including scape) 30-40 cm long........................................................ D. brevicornis

10 Petiole oblanceolate ................................................................................................................... 11
10 Petiole linear ............................................................................................................................... 12
11 Inflorescence (including scape) up to 18 cm long; pedicels
3-7 mm long ................................................................................................... D. dilatato-petiolaris
11 Inflorescence (including scape) up to 45 cm long; pedicels
1-2 mm long ........................................................................................................................D. fulva
12 Inflorescence (including scape) glabrous .............................................................. D. broomensis
12 Inflorescence (including scape) covered with woolly hairs ....................................... D. petiolaris



Identifying species through 1 or 2 photographs is difficult. Not enough of the fine detail may be visible and the angle may not show if the leaves are semi-erect or not. This also illustrates the pitfalls of trying to identify species by comparing your plants to photographs. The appearance of a plant can vary tremendously due to the age, health and growing conditions. And often the photos are mislabeled or the plant pictured incorrectly identified to begin with.

Sean Spence however is someone whose opinion on Drosera ID I well respect. He has the years of experience and expertise to be able to eyeball species from photographs with a high degree of accuracy. He is a member here, though seldom posts these days.

It would also appear from the above key the inflorescence on D. dilatatopetiolaris is much shorter than D. petiolaris - only up to 18cm
 
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  • #11
thanks a lot NaN. so basically the real tell tale sign would be inflorescences based on the key.
 
  • #12
A qualified es, unless there is a newer key.

I guess if it doesn't fall into Lowrie's key it is either a hybrid or an affinis.
 
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