Category: Friday puzzle

Friday puzzle solved – better late than never!

I spent yesterday flying from Seattle to Buffalo and didn’t get a chance to post the answer to the puzzle on Friday.  This was an easy one for our readers – the shrub is (was?) a mesquite, and the bushy growth in the photograph is mistletoe (as identified by Bob and seconded by Ginny and Jimbo). 

I am pretty sure this mesquite was dead, as it had been a wet spring and everything was leafing out.  That being said, I didn’t cut into the bark to find out.  If it is dead, that does raise the fascinating question of how the mistletoe can extract water from a dead shrub.  So it’s likely that the mesquite is just slow to leaf out.

This (and other) mistletoes provide food for native birds, and as Jimbo points out they are the perfect dispersal mechanism for the sticky seeds.  There’s a great video of this behavior in the "Secret Life of Plants" by David Attenborough – if you haven’t seen this series, you should.  Amazing.

Thanks, all, for playing – and Peter, your last comment was perfect!

Morphology quiz answers

As Jason rightly guessed, this is a Schlumbergera species, specifically S. truncata, also known as the Thanksgiving cactus (which has toothed edges as shown). It’s related to the Christmas cactus (S. bridgesii – scalloped edges) and the Easter cactus (S. gaertneri, whose segments are three-sided rather than flattened). [Disclaimer: the nomenclature of this genus and its species is a mess. Even the university websites disagree on whether it’s Schlumbergera, Hatiora, or Rhipsalidopsis. Now you know why I am not a taxonomist.]

On to the more interesting question – those hairs. The green segments you see on these plants are not leaves, but flattened stems, called phylloclades (or cladodes). Phylloclade comes from the Latin word for leaf (phyllo-) and the Greek word for branch (-clade). These leaf-like branches are the primary photosynthetic organs for the plant.

So where, you may ask, are the leaves? That’s what those hairs are! And if you look at your Christmas/Easter/Thanksgiving cactus when it begins to set buds, you’ll see that the buds arise from the leaf axils – that point where the leaf joins the stem. This distinction is why these hairs are, morphologically, the true leaves of the plant.

Flower demystification

As Paul suspected, this is a Phalaenoposis flower.  Here it is again, shown next to another flower on the same plant (but different stalk):

  

As to the second question – why does it look this way – there could be a number of reasons.  I’m leaning toward environmental.  This particular flower stalk is an old one – after it had bloomed initially (with normal flowers), we left it on after the flowers fell.  As often happens, new flower buds appeared, but all of them have been abnormal.  Some were completely fused and never opened.  This one is missing most of its petals.

Other reasons could include viral infection (as Sheila suggested) or somaclonal variation (common in tissue cultured plants, which is how many orchids are propagated).  But this flower stalk is perpetually colder than the rest of the plant as it’s closest to the window.  And since its first crop of flowers were normal, I think this variation is due to cold temperature interference during flower development.

If you have other ideas, be sure to post them!

Friday puzzler unearthed!

Lots of good guesses this week! As many of you realized, this is a huge tree root making the best of a small tree pit.  But it’s not a Norway maple (sorry John) or a mulberry (sorry Robert), but a sweetgum (Liquidambar styraciflua) (congratulations Brian!).  (You can see the little mace-like seed pods on the ground.)  The root does resemble a bicep (“Treebeard’s elbow”) flexing to crack the concrete (aka Robert’s  Concretious blandmulsia):

Though sweetgum can be nice urban trees, their roots are quite vigorous and can lift sidewalks several inches above grade as they increase in diameter:

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Thanks for all the entries – our readers are smart and funny!

Short tree syndrome solved!

Good answers from Kenny S., Jimbo, Joe Schalk and Diana!  You were all skirting about the phenomenon of thigmomorphogenesis – or touch-induced change (also discussed in Jeff’s post of January 7.  The tests in the GP’s class are cumulative!).  In this case, the touch is wind.  Edge trees (or corn stalks) are more exposed and receive more wind, resulting in stunted heights and increased trunk diameter (you can’t see this last characteristic in the Friday photo).  Trees in the middle of the stand aren’t exposed to wind buffeting and put their resources into increased height. Similar stunting and thickening can be seen in urban plantings along the edges of sidewalks or anywhere people or animals routinely walk.

I spent my grade school years in a 1950’s housing development that had been Douglas fir (Pseudotsuga menziesii) forest.  The developers left many of the trees standing, and our backyard was full of tall, skinny and isolated Douglas firs.  When the Columbus Day storm (an extratropical cyclone, of all things) hit the Pacific NW in 1962, seven of these trees came down (none hit our house, fortunately).

Now of course a cyclone will take down many trees, regardless of their location…but this continued practice of leaving trees standing alone during development often results in blowdown or breakage of these now unprotected trees.