Marion Holmes's picture

Daisy like flower

Observed: 28th September 2011 By: Marion Holmes
Marion Holmes’s reputation in PlantsMarion Holmes’s reputation in PlantsMarion Holmes’s reputation in Plants
petrusdal 28sep11 c ispot

Taken at an altitude of approximately 1581m on Nardou in the Agtersneeuberg Mountain range.

Species interactions

No interactions present.

Species with which Witgousblom (Dimorphotheca cuneata) interacts


Tony Rebelo's picture

Please dont hide localities!

Please dont hide localities!

Marion Holmes's picture

I hid the localities for this

I hid the localities for this property as they (flower submissions) were not posted with the owners permission. This is one of my research sites (for diatoms) and I only have his permission for that. Many farmers would not be happy with information collected on their properties being released.

Tony Rebelo's picture


But if the farmer is not happy, why post it? How does hiding this address the issue?

Sorry, I see a potential issue here. Please rather get permission if you think the owner might object and you wish to retain a cordial relationship. I can understand if the owner is doing something illegal that you wish to surreptitiously make known. But otherwise rather try and circumvent issues with permission than by hiding the locality.

Marion Holmes's picture

Farmer gave permission for

Farmer gave permission for his location to be listed.

Tony Rebelo's picture


Thank you very much: I appreciate the trouble you have gone to.
Always good to keep things above board whenever possible.

Lee Jones's picture


rather like one of the Dimorphothecas

Wynand Uys's picture


As water quality indicator?
Please tell us more..

Marion Holmes's picture

sorry for the delay in

sorry for the delay in replying. Diatoms have been successfully used overseas for many years as a biomonitoring tool for water quality. The research is much newer in SA. I am lucky to have the diatom fundi in SA as my study supervisor! I have been monitoring the upper reaches (spring water) of the Great Fish River since the beginning on 2010. This requires diatom samples as well as physical variables of the water be taken at intervals. Chemical water analysis is run on water samples to confirm what the diatom community is showing (for my project). All very interesting - amazing how 100+ years of agriculture has affected the water quality.

Tony Rebelo's picture

So when dare we

So when dare we expect stunning electro micrographs of beauteous diatoms displayed in all their glory?

Wynand Uys's picture

Thanks, and yes:

Exactly what I was going to ask. Obs please!

In the meantime I've been reading up about diatoms as biomonitoring indicators. Really useful! Pity the ID's can't be done in the field.

What order of (light microspcopy) magnification is required to make ID's of the skeletons once they've been cleaned up?

Riaan Stals's picture

Yes! Diatom photos!

Please post us a selection of common genera! Pretty please.


Marion Holmes's picture


Haven't been able to get SEM pics (how I wish!)- I am over 800km away from my university I have had to set up a mini lab on the farm. I do id's with a phase contrast microscope on loan. Id's to genus level can sometimes be made under 40x but for species level you need at least 100x (phase). It is very difficult to see the ornamentation clearly with brightfield. In addition to phase I also use a green colour filter to improve the contrast for id. This results in a type of greyscale photo.

Cleaning the frustules is a time consuming job (and quite a smelly one) involving boiling, acids etc.

Id to species level for certain diatoms (Nitzschia) is extremely tricky. When the frustules show deformities it is even trickier!

Marion Holmes's picture


Posted 2 photos - Sellaphora pupula and Craticula buderi meantime. There are some others that are truly spectacular to look at.

Tony Rebelo's picture


Brilliant: looking forward to seeing them and more!!