The eastern members of sect. Alectoroctonum

Section Alectoroctonum is a section of New World Euphorbias that is generally distinguished from many other groups by having petal-like appendages and not possessing any particular specialized characteristics. The group is quite diverse and may form herbs, shrubs, or even succulents (see E. antisyphilitica). They are so diverse that the seem to hold the middle-ground between many of the better-defined groups of US Euphorbias like sect. Anisophyllum and subg. Esula. They generally have dichasial branching like members of subg. Esula, but the bracts are generally similar enough to the stem leaves that they evade notice (except in species like E. marginata). They generally have alternate leaves below, but some have lower stems so reduced so as to only produce opposite leaves (see E. macropus). Furthermore, the group may be confused with members of sect. Nummulariopsis. Section Alectoroctonum is best learned by simply learning the main species in the group and comparing to others outside the group. There is some continuity, but it is difficult to define.

Here, I am considering the species in states east of Texas. Observations from the area.

Euphorbia marginata

Photo credit: Sam Kieschnick (click here for observation).

Euphorbia graminea

Photo credit (left): Jay Keller (click here for observation). Photo credit (right): Jay Keller (click here for observation).

Euphorbia polyphylla

Photo credit (left): Jay Keller (click here for observation). Photo credit (right): Jay Keller (click here for observation).

Euphorbia ipecacuanhae


Photo credit (upper left): Rob Van Epps (click here for observation). Photo credit (upper right): Michael Ellis (click here for observation).
Photo credit (lower left): Jason Hafstad (click here for observation). Photo credit (lower right): Joshua Tewksbury (click here for observation).

Euphorbia exserta

Photo credit (left): ericpo1 (click here for observation). Photo credit (right): Jay Keller (click here for observation).

Euphorbia mercurialina

Photo credit (left): Erin Faulkner (click here for observation). Photo credit (right): Jonathan (JC) Carpenter (click here for observation).

Euphorbia curtisii


Photo credit (upper left): Andy Newman (click here for observation). Photo credit (upper right): jtuttle (click here for observation).
Photo credit (lower left): whiteoak (click here for observation). Photo credit (lower right): whiteoak (click here for observation).

Euphorbia hexagona

Photo credit: Brush F (click here for observation).

Euphorbia corollata complex
The photos bellow appear to represent true examples of their respective species. However, many populations are very difficult to determine. Some seem intermediate while others seem to represent distinct entities. There is at least one undescribed species represented in this group.

Euphorbia discoidalis

Photo credit (upper left): cwarneke (click here for observation). Photo credit (upper right): howardhorne (click here for observation).

Euphorbia pubentissima

Photo credit: Janet Wright (click here for observation).

Euphorbia corollata


Photo credit (upper left): Janet Wright (click here for observation). Photo credit (upper right): Alvin Diamond (click here for observation).
Photo credit (lower left): Kit Howard (click here for observation). Photo credit (lower right): Nathan Taylor (click here for observation).

References to look into:
https://link.springer.com/article/10.1007/BF03030498
https://www.tandfonline.com/doi/abs/10.1080/00173139709362584
https://www.journals.uchicago.edu/doi/abs/10.1086/297457

Posted by nathantaylor nathantaylor, May 06, 2019 04:23

Comments

No comments yet.

Add a Comment

Sign In or Sign Up to add comments

Is this inappropriate, spam, or offensive? Add a Flag