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Excerpts from Jim Conrad's
Naturalist Newsletter
Entry from field notes dated July 1, 2023, taken along small gravel road between El Suspir and Curva de la Doctorcilla, about 1 straight-line km north of El Doctor; in mountains of east-central Querétaro state, municipality of Cadereyta de Montes, 12 straight-line kms due east of Vizarrón de Montes but much farther by twisting roads; elevation ~2600m (~8500 ft), Querétaro, MÉXICO, (N20.85563°, W99.58686°)
ARRACACIA TOLUCENSIS
On a steep, northeast-facing slope the slender, stiff-stemmed, somewhat rawboned-looking, meter-tall plant at the right grew at the base of a vertical limestone outcrop. It was a dry location most of the day shaded by pines and oaks. One wondered how such substantial stems, which were not woody despite their straightness and thickness, could form without conspicuous leaves. However, the leaves were there, toward the base, just with very slender leaflets. Atop the stems grew flat-topped flower clusters as seen below:
Numerous tiny flowers were clustered atop stalks, or rays, radiating from a single point atop a common stalk, or peduncle. This was a classic compound-umbel-type flower cluster. Here's what the above umbel looked like from below:
Spiders had found this umbel a congenial place for their webs. Only a few plant families are capable of producing such umbel-type inflorescences, and the main family to think of when you see them is the Umbellifer-Parsley-Celery Family, the Apiaceae. Typically in this family, just below the point on the peduncle where the rays arise, there's a collar of modified leaves, or bracts, known as the involucre. Our plant has no involucre, or even bractlets at ray tips below the clusters of individual flowers, the umbellets, and that absence is a good field mark. The many whitish, grainy items are anthers discarded after they'd released their pollen. Each umbellet bears a few green, developing fruits, better seen below:
These are immature schizocarp-type fruits, schizocarps being dry fruits which when mature split into single-seeded parts called mericarps. Above, the tallest schizocarp is topped by fading flower petals. The second-tallest schizocarp is topped by the remains of two styles. At the style base there's a swelling before the fruit begins, the stylopodium, which in many species secretes nectar. Schizocarps in this family normally are ribbed. All these fruit features are typical of the Parsley Family, as opposed to the few other families producing umbels.
Above, it's seen that this plant's leaves are compound -- divided into distict parts. At the picture's top, the stem rises from the ground, then three stalks depart from a single point. This is the first subdivision, for the two stalks, or rachillas, rising diagonally as they leave the picture each bear a primary leaf division like the one occupying most of the picture. Over my hand, one of the three primary divisions is subdivided, and those subdivisions are subdivided into slender leaflets. This plant, then, at least near the base, bears 3-pinnate compound leaves. The three primary stalks arise from a conspicuous, inflated petiole which at its base wraps around the plant stem:
The brown cluster of stamens below the three rachillas has been dropped from an above umbel.
In this part of upland central Mexico if you have a meter-tall (yard) member of the Parsley/Umbellifer Family with compound leaves divided three times, bearing very slender but not threadlike leaflets, umbels which are compound and not subtended by a conspicuous involucre, and schizocarps bearing no spines and which are oblong, not egg-shaped or wider, you have the genus Arracacia. We've met a member of that strictly New World genus before, Arracacia aegopodioides, a species adapted for moister conditions, and producing much broader leaflets, than our limestone outcrop plant.
The genus Arracacia comprises about 41 species occurring from Mexico to Bolivia. Its most famous species is the Arracacha, a starchy root vegetable from the Andes, somewhat like rutabaga, and poplar across South America. In our area, if you have an Arracacia with flat-topped umbels not subtended by involucres, you have ARRACACIA TOLUCENSIS.
Arracacia tolucensis inhabits highland oak/pine forests from central Mexico south to northern South America. The species name tolucensis derives from the highland city of Toluca found just west across the mountains from Mexico City. The taxon was introduced to science by a collection made by Humboldt and Bonpland during their visit to Mexico during 1803 and 1804. Their collection is annotated, "crescit locis alpinis Novae Hispaniae, inter Tolucam et Islahuacam" -- "grows in alpine areas of New Spain, between Toluca and Islahuaca." I'm guessing that Islahuaca is what now is called Ixtlahuaca.
In Mexico, Arracacia tolucensis is regarded as medicinal, one use being to treat diabetes. In a 2013 study by Mary Carmen García Galicia entitled "Efecto de tres extractos de Arracacia tolucensis en ratas diabéticas inducidas con stz," it was found that an extract of Arracacia tolucensis produced a hypoglycemic, or blood-sugar lowering, effect on diabetic rats without otherwise affecting the rats' biochemical and cellular morphology. The 2010 study by María Adelina Jiménez Arellanes and others entitled "Las plantas medicinales mexicanas como fuente de compuestos antimicobacterianos," found that extracts from above-ground parts of our Arracacia tolucensis inhibited the growth of Mycobacterium tuberculosis bacteria, which causes tuberculosis.