Succulent Sunday has been on hiatus while Mr Sentient Meat is out of the country. Plans are to resume upon returning to Los Angeles. —SM

In this terrific little video, renowned psychiatrist and writer Iain McGilchrist first explodes once-fashionable ideas about the left and right brain which held sway from the 60s to the early 80s. After thoroughly demolishing the traditional splits (reason/imagination, verbal/spacial), he takes a surprise turn and tells us how these hemispheres really do have qualitatively different roles after all. Finally he takes in the full sweep of history and points out our near-worship of the fruits of the left brain… to the detriment of society. A fascinating grand tour: heavy on vision, very light on references. Fortunately, he makes a persuasive case that if we take the concepts from this talk, we can go explore the literature for ourselves and confirm what research is continuing to reveal about the divided brain.

Lithops sp, tentatively L marmorata, on 2nd day of bloom. The largest body here is under 2 inches at its widest.

When you walk down the aisle of a plant show or even a nursery department in a big-box store, certain succulents reach out and knock you over. They barely look like plants. In fact, sometimes it’s hard to believe they’re even alive. Lithops are tiny but they fall into this drop-dead category.

With a name from the Greek for stone and eye or face, Lithops or “Living Stones” are small plants native to the dry Western Cape region of Southern Africa. They are in the same family (Aizoiaceae) as ice plants, also originally from Southern Africa and spread the world over by human travel and other transport.

Unlike their cousins the ice plants—cultivated for centuries and easy to care for—Lithops are widely known only since the 1950s (with the collecting and cataloging work of Desmond and Naureen Cole). Not only did they emerge from obscurity recently — they also have a reputation for being somewhat difficult for amateur cacti and succulents growers. (I have killed quite a few of them, and the Lithops flowers pictured are some of my first.) Lithops are adapted to a dry existence, and if watered too much or at the wrong time they can succumb quickly to that omnipresent nemesis of succulent fanciers: rot.

Lithops care is less of a puzzle once you learn a basic lesson about about their special needs in winter: briefly, don’t feed or water them. They are not truly dormant, but they are busy with a small, vital, inner task: growing a new leaf pair in the center of the plant. As the new pair (or pairs) grow, they absorb the nutrients from the previous year’s pair. The outer pair shrivels and the inner pair (or pairs) emerges from the seam between the two dying leaves. If you water them during this period, you risk rotting the plant or preventing the outer leaves from being absorbed. Even if the plant survives, this can lead to a misshapen and unnatural look, living blobs instead of neat roundish tiles.

Mid-October, the time of this post, is prime time for Lithops flowers. They like to make hay while the sun still shines.

References

Lithops gallery

Lithops.info

Cole, Desmond; Cole, Naureen (2005). Lithops—Flowering Stones. Cactus & Co. 368 pages (20.7 × 29.5 cm), 644 col. + 5 b/w photos, 3 col. + 85 b/w drawings, 7 maps, 98 habitat photos. ISBN-10 88-900511-7-5. ISBN-13 978-88-900511-7-3

Hammer, Steven (2010). Lithops: Treasures of the Veld. 2nd Edition. BCCS. Softbound; 156 pages; 238 photos. ISBN-10: 0902099922. ISBN-13: 978-0902099920.

Shimada, Yasuhiko (2001). The Genus Lithops. Dobun Shoin. 240 pages (19 × 26.5 cm), 437 col. photos, 1 b/w map. ISBN-10 4-8103-4066-X.

Revisiting Mammillaria hernandezii in October, this time in bloom

On a recent Succulent Sunday we saw Mammillaria hernandezii. I wrote about its relatively large, purple-pink flowers, but since a picture is worth at least as many words as I wrote, here’s a follow-up. This was the first flower; if you look closely you can see the conical buds for more flowers to come. Also see how the smaller head has grown much larger in 3 months.

The same plant(s) from back in July. Besides the bloom, notice how much smaller the second head was.

You can’t wade very far into the study of evolution, plant taxonomy — or the pursuit of growing exotic succulents at home — without smacking right into convergent evolution. That’s the notion that certain distantly related plants have evolved features which make them seem much more alike than their DNA (or evolutionary pedigree) would predict.

Hoodia pilifera, 3.5″ tall, like a tiny saguaro South Africa (Western Cape, Little and Great Karoo) photo by Sentient Meat

As I’ve learned more about it, I’ve come to the conclusion that there are two kinds of convergent evolution: the superficial, obvious kind and the subtle, fool-a-scientist kind. The more subtle kind of convergent evolution — the kind that can fool a scientist — shows up in the study of plant taxonomy (the classification of plants into species, genus, and family based on how closely they’re related). Just as DNA science has revolutionized how crimes are solved (and revealed that some imprisoned felons are actually innocent), the study of DNA in plants has revealed that plants once believed by scientists to be closely related (due to similarities in stem, leaves, flowers, or seeds) are actually quite distant relatives. They developed their similarities independently — and well after their ancestors had split off from each other. As a result, the family tree (for example, of Euphorbia¹) has been in a state of ongoing upheaval as the contemporary field of molecular phylogenetics revises our knowledge of evolutionary relationships and reveals many cases of subtle, scientist-fooling, convergent evolution.

Actual saguaro, approx 100x taller than our H pilifera photo by Leonard G. / Wikipedia – Creative Commons ShareAlike 1.0 license

In grade school we learn the more obvious kind of convergent evolution — a sort of gee-whiz, ain’t-Nature-grand, intercontinental shape-matching game, in which we are amazed that plants from Africa (like spiny euphorbs and today’s feature, Hoodia pilifera) bear such a striking, if superficial, resemblance to desert cactus (like the majestic saguaro, pictured), which hail exclusively from the Americas.
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In my yard, I tend to overlook Thelocactus bicolor until it blooms. Its body is green, moderately spiny and round — about 3 inches across in this particular young plant (globose… or actually ovoidal in this beautiful technical summary on Thelocactus). The problem is, hundreds or thousands of cacti fit a similar description, including dozens under my care.

When it does bloom, “The Glory of Texas” is impossible to ignore. From a distance the bright magenta petals catch your eye (faded to pink here by my cheap camera). Something about the deep crimson center and glistening yellow pollen also jumps out at you, even from 10 yards away… not to mention the bloom’s size: on the young plant pictured, the flower is an inch wider than the entire body of of the plant.

Thelocactus bicolor is widespread in the deserts of Texas and northern Mexico (see the excellent map of its known habitat from the Thelocactus site), so it’s in no danger of disappearing… either from habitat or from admiring eyes of home growers.

Thelocactus bicolor is widespread in Northern Mexico shown on this beautiful map at http://www.thelocactus.cactus-mall.com/Thelocactus_Site.html