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Thursday, December 20, 2012

The basic taxonomy of a Portulaca plant

Let's start with some very basic taxonomy. Although the initiated among us may find this all a bit tedious, I feel it is probably necessary to get some basic botany out of the way before proceeding any further.

Pictured here is a rather generic Portulaca plant showing its main parts (click on image to enlarge).

The leaves and stems of Portulaca are generally fleshy or succulent with a mostly smooth (i.e. glabrous) surface. Plants are generally prostrate or decumbent, but some species may be upright or ascending. Some species may have prominent hairs in the leaf axils. Flowers range from being small and inconspicuous to large and showy. Flower colour may vary from species to species, but the three most common colours are pink, purple, and yellow. The roots may be tuberous or fibrous and the different species may be perennial or annual.

The seed capsule is technically called a pyxis. Here is some good information about Portulaca fruiting capsules from an Illinois Natural History website.

The pyxis is in two parts and resembles the fruiting body of a Eucalyptus tree (i.e. a "gum nut"). It comprises a lower capsule which holds the seeds and an upper lid (or operculum). The lid separates near the middle of the pyxis and falls off (dehisces) when ripe to spill out the seeds.
Parts of a Portulaca pyxis by Leo Breman (ex flickriver).

Jim Conrad's Naturalist Newsletter also illustrates this well.

Generally the seed is numerous, fine, and granular. Under magnification it is shaped a bit like a snail shell or a flattened spiral. The surface is often rough and covered in tiny stellated (or "star-like") tubercles. Seed of Portulaca oleracea (ex AcornOrganic, Steve Hurst, USDA)


4 comments:

Robert said...

Great to see your new blog spring to life Ian, look forward to reading more posts. Cheers, Rob Ashdown.

Attila Kapitany said...

On first impressions it looks great. Hope it continues with success. I will endeavour to contribute occasionally and will put a mention into the next cactus and succulent society journal of Australia.
Attila

grey_gum said...

Thanks Rob, I hope to introduce some of the common native species before moving on to some of the less common and indeterminate plants. Then move on to species found in other countries, such as the interesting Portulaca molokiniensis from Hawaii. Other native and exotic plants will also be covered from time to time. I do not intend to limit my posts entirely to Portulacaceae by any means.

grey_gum said...

Attila, I am looking forward to receiving your photos which will be invaluable. Thank you for mentioning the blog in the C&S journal. This is greatly appreciated.