Friday, February 15, 2013

Portulaca oligosperma

Portulaca oligosperma F. Muell. (1859) is another of the tropical annuals with opposite leaves and pink-purple flowers. It is prostrate and forms mats to about 100 cm wide. It flowers from February to May.

It grows in woodlands on sandy or loamy soils from the Kimberley region in WA to Normanton in Queensland, with several sporadic records in eastern tropical Queensland (west of the Mulligan Highway).

P. oligosperma is similar in some respects to P. digyna. It differs from that species by:
  • 6-petalled flowers, cf. 4(-5) petalled for P. digyna.
  • 6 stamens and a 3-lobed stigma, cf. 4(-10) stamens and a 2-lobed stigma for P. digyna.
  • common style about as long as the stigmatic arms, cf. common style longer than stigmatic arms for P. digyna
  • capsule operculum conical and glabrous, cf. turbinate and papillose for P. digyna.
  • seeds grey, tuberculate, cf. black and smooth for P. digyna.

Another difference is that the branch segments of P. oligosperma have a slightly divaricating, flexuous habit. This means that the segments of each branch diverge from each other on a slight angle from the nodes, giving the branches a characteristic "zig-zag" habit.

The only photograph that I can find of this species is on the Atlas of Living Australia website.


joseph holtum said...

Ian, in your sectionon differences between oligosperma and dignya, your oligosperma characteristics of petal number and stigma lobes differ from those recorded by Eggli. Any comments?

grey_gum said...

Hi Joseph, I can't really comment as I have never seen P. digyna or P. oligosperma, and I doubt whether Eggli had ever seen them either. Both of us are just going by what someone else has described. I often find that field observations show marked differences to the taxonomic descriptions. Portulaca taxonomy is a mess.

grey_gum said...

I recall my descriptions came from Mueller.