Grasses - my second study, Hordeum murinum

The first was one I have seen in many places before, so I didn't feel bad about collecting it. It turns out to be Hordeum murinum or "wall barley". I identified it using the "leaf" method, i.e. I picked up two of my books and leafed first through one, then through the other looking for a photo or drawing that matched. My first book (with nice pictures) was the "field guide to Grasses of California". It let me down because H. murinum was not pictured! The second book was "A field guide to the Grasses of New Mexico". It has line drawings and I struck it rich. I am not yet ready to use keys to identify grasses. I am still coming to grips with what lemmas and florets and glumes are, and want to be able to study known plants to build some confidence that I know what is what.

Once I thought I recognized it in the New Mexico book, I did an online search for Hordeum murinum and looked at many photos, which confirmed my identification. Then I went back to the California book and discovered that the species is listed, but not photographed. I hauled out my copy of Arizona Flora (Kearney and Peebles) and discovered that H. murinum is not listed under Hordeum. I am no longer surprised by this. Botanical nomenclature is in a constant state of upheaval and it is rare to find a plant that has kept the same name for over 50 years. Kearney and Peebles call this plant Hordeum leporinum.

Now that I have descriptions, I can read them and see if I can recognize features in my plant. K and P say it is "a weed in cultivated land and waste places, introduced from Europe". Three grasses so far, and not a native species yet.

The New Mexico book calls the inflorescence a "bristly spike", which sounds about right. Spikelets are born in threes, the central sessile and the lateral pedicelled. Each spikelet in the trio has two glumes that extend into a long awn. The lemma also extends into a long awn, longer and more prominent that the awn from the glumes. As the book says, the glumes have "conspicuous ciliate margins", which is true. One of the glumes (the one towards the center) on each of the lateral florets also has ciliate margins -- the other lacks cilia.

There are two subspecies, distinguished by the color of the anthers in the central spikelet. Variety "glaucum" has blackish anthers, while variety "leporinum" has yellowish anthers. My specimen is already going to seed, so there are no anthers to look at. The other thing to look at is the "prolongation of the rachilla of the lateral spikelets". If it is stout and orange-brown it is "glaucum", if it is slender and greenish, it is "leporinum".

I would have called the plant caespitose (i.e. "bunched"). It is reputed to be an annual. The leaves have auricles. On my specimen only the central floret seems to be developing a seed, but that may be coincidence.

Now, let's run one of the keys backwards and see what path would have brought is to Hordeum. Let's use the California key, and I will describe it as if I was working it from the start. The first choices in the California key simply eliminate some unique genera. Then we get to question 6 -- spikelets one or two in an inflorescence or few to many. Clearly the second choice since we have many florets in the spike. More choices eliminate some unique genera, then we get to question 11, which asks if the plant is more than 15cm (6 inches) tall. Mine is a good 12 inches (use a ruler, don't rely on memory or guesses), so on to question 12. Question 12 is whether spikelets are subtended by bristles. This could be confusing since my glumes could be called bristles, but they are part of the spikelet, not subtending it, so we are on to 13. Question 13 asks if the glumes and/or lemmas are covered by prominent silky hairs (no). Question 14 asks if the glumes or lemmas have 3 to 9 awns (sorry, mine only have one awn each), so we are on to 15. Question 15 asks if the spikelets are dorsally or laterally compressed. My plant has laterally compressed spikelets, taking me to question 17. This asks if there are distinct different spikelets or if they are all the same. I have two sorts of spikelets. I have a central one and the two lateral ones, so I am on to "Group 10".

Now the group 10 key. The first question is whether there are separate staminate and pistillate spikelets. I can't say for sure since my plant is past that stage, but I say no. Question 4 asks if the inflorescence is a spike or panicle. Mine is a spike. Do I have one spikelet per node or three? I have three. One last question -- are the stem internodes hollow or solid? A quick cut with a razor blade and a peek under the microscope shows they are hollow, hence Hordeum.

Well, perhaps I could have navigated that, but it would be difficult to feel confident at this stage of my learning.