Mexican Palmatipinnate

E. prostratus	E. rotundifolius	E. purpusii

Mexican Evolvulus Taxa with Palmatipinnate Venation

by Bob Harms email-here

Four taxa which I have been able to examine are shown below.

Collections of the following three somewhat similar Mexican taxa with somewhat modified palmatipinnate venation (i.e., with greater variation than I have observed with E. sericeus) have at times, in my opinion, been confused. Additionally I have seen all three determined as E. sericeus, perhaps based on their shared feature of a glabrous upper leaf surface and lack of familiarity with van Ooststroom's 1934 monograph. Details of their venation might prove useful to distinguish them, listed with the descriptions given by van Ooststroom, these are:

Evolvulus prostratus
midrib and 2-3 pairs of lateral nerves, rising from near the base, impressed above, more or less prominent beneath
Evolvulus rotundifolius
midrib and 2-3 pairs of lateral nerves, rising from the base, impressed above
Evolvulus purpusii
midrib impressed above, other nervation invisible

[click on images below for enlargement]

Evolvulus prostratus

E. prostratus has strong secondary basal acrodromus venation, with no pinnate secondary veins visible, on both leaf surfaces, with two or more pairs of secondaries arising from a broad petiolar base — very similar to E. discolor, with secondaries arising elsewhere not common. Additionally the veins on the lower surface are typically prominently raised.

Durango	Jalisco

Estado de Mexico	Jalisco

The venation of this specimen would seem to suggest that it is not E. prostratus (Michoacan). The leaves have weak variable venation, unusual even on this plant in that secondaries are not paired from the very base, although they are all directed upward toward the apex.

Evolvulus rotundifolius

E. rotundifolius differs from the above in its much weaker secondaries, barely visible on the lower surface, and with strong secondaries commonly arising along the midrib on the lower half of the leaf. Although it has blue corollas — a key feature distinguishing it from E. prostratus — these fade to pale/yellowish white with age and could be the source of some confusion.

Image on right is the area in the yellow box on the left. Durango..

Both images from the same Durango collection as above.

Three E. rotundifolius leaves from the same plant (Durango). A & B show the two paired secondaries arising from the base (the outer pair questionably secondary, shorter and weaker) with no secondaries above these; C is quite different with secondaries not paired and not limited to the very base, although all secondaries are directed toward the apex..

E. rotundifolius leaves from three areas. The Durango and Chihuahua secondaries are all directed toward the apex, even those at the mid point. With Sonora the higher secondaries close loops withs veins from lower down. .

Evolvulus purpusii

The secondaries of E. purpusii are never visible on the pubescent lower surface, and frequently invisible (as noted by van Ooststroom) or only barely visible on the upper surface. Without evidence from transmitted light, determining a palmatipinnate pattern would be extremely difficult. Below right are three images of the same leaf, two were made with transmitted light through the rehydrated leaf.

Nuevo Leon.

Evolvulus choapanus

E. choapanus linear–lanceolate leaves, from JSTOR scan of isotype at MEXU .

In A New Species Of Evolvulus (Convolvulaceae) From Veracruz, Mexico [Phytologia 65:152-3 (1988)], A. McDonald includes the following description:

Leaves ... lamina linear–lanceolate, 1.0—1.8 cm long, 2—3 mm wide, ... venation palmate with 3-5 major nerves.

In his 1993 article "Evolvulus" in Flora de Veracruz, McDonald has an apparent contrast of E. choapanus with E. sericeus, the former said to have "venación palmada, 3—5 nervaduras mayores saliendo de la base" [i.e. palmate, 3—5 major veins originating from the base] the latter, "venación palmattipinada, las 3 nervaduras mayores originándose desde las base" [i.e. palmatipinnate, the 3 major veins originating from the base].

Attempts to find venation patterns on the JSTOR scanned leaves has proved futile. Subsequently I was able to view an isotype specimen on loan from the Field Museum (A.D.L. Orozco S. 188). Leaves of this specimen were palmatipinnate, as were leaves of E. sericeus from Veracruz. No leaves were found with strictly palmate venation. In general the venation of this isotype was somewhat stronger than with the E. sericeus specimens from Veracruz at the Field Museum — not however, stronger than E. sericeus specimens from other areas. [Click on image for enlargement.]

Leaf of E. choapanus isotype with pinnate secondary veins (red arrow), some below the midpoint.

Leaf of E. sericeus (S. Avendaño A-223, det. by A. McDonald) from Veracruz with a pair of secondary veins
extending from the base, and no pinnate secondaries visible.

Backlit leaf of E. sericeus, Hays Co.,Texas, with a pair of secondary veins extending from the base,
and no pinnate secondaries.

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