Journal archives for May 2019

May 06, 2019

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. Click on the species name in bold to see observations from the area verified by me.

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 (photos here) 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:
Monograph of Euphorbia sect. Tithymalopsis(Euphorbiaceae)
A New Species of Euphorbia Subgenus Chamaesyce Section Alectoroctonum (Euphorbiaceae) From Limestone Hills of Wayne County, Mississippi
Seed morphology ofEuphorbia sectionTithymalopsis (Euphorbiaceae) and related species
Pollen morphology of Euphorbia subgenus Agaloma section Tithymalopsis and related species (Euphorbiaceae)
Isozyme and Morphological Divergence Within Euphorbia Section Tithymalopsis (Euphorbiaceae)

Posted on May 06, 2019 04:23 by nathantaylor nathantaylor | 0 comments | Leave a comment

May 28, 2019

A few members of subgenus Esula sect. Helioscopia

These plants have serrated leaves and glands without appendages. According to Euphorbia PBI, there are about 180 taxa. To go through them all would be very time consuming and well beyond the scope of this project. However, in order to better understand the species that have been introduced to other locations, it is worth discussing a few outside the US that have spread outside of Afroeurasia where most species are native. Notes on leaves refer to the lower leaves and usually includes the similar pleiochasial bracts, but not the dichasial bracts (click here for notes on the bracts). Plants known to occur in New Zealand are marked "NZ" at the end. Plants known to occur in the United States are marked "US" at the end.

E. oblongata - Perennial; stems villous; leaves glabrous, ranging from oblong, elliptic, to broadly lanceolate or ovate, not linear or linear-lanceolate, typically broadest at the base or middle but may be broadest at the apices, apices rounded; glands typically 2-3 (typically 2 in dichasia); fruits warty. Originally from Eurasia, but introduced elsewhere. NZ US
E. depauperata - Perennial; stems glabrous or pilose; leaves glabrous or occasionally pilose, typically linear-lanceolate, sometimes slightly broader, apices typically acute; glands 4-6; fruits warty. Africa.
E. epithymoides - Perennial; stems villous; leaves pilose; broadest towards the middle or base, apices rounded; glands 2-5 (even in same inflorescence) but most commonly 4; fruits covered with many narrow, hair-like warts. Originally from Eurasia, but introduced elsewhere. US
Annuals - Many of these are quite difficult to distinguish and may require seed characteristics.
E. platyphyllos - Annual; stems usually glabrous; leaves glabrous or hairy, usually oblanceolate, typically broadest at apices, apices acute; many dichasia produced before terminal pleiochasium of 3-5 branches; glands 4; fruits warty; seeds smooth, over 2 mm long. Two forms: 1. plants glabrous, more common. 2. plants hairy, less common (specimen 1; photos). Type much more robust than most specimens representing the species. Originally from Eurasia, but introduced elsewhere. NZ US
E. stricta - Annual, glabrous; leaves usually oblanceolate, typically broadest at apices, apices acute; many dichasia produced before terminal pleiochasium of 3-5 branches; glands 4; fruits warty; seeds smooth, under 2 mm long. Two forms: 1. leaves sharply acute, margins sharply serrulate; dichasial bracts mucronate; fruits warts shorter (specimen 1; specimen 2). 2. leaves less sharply acute, margins less sharply serrulate; dichasial bracts mucronate or commonly not; fruit warts long (photos; specimen). Misidentifications? Originally from Eurasia, but introduced elsewhere. NZ
E. spathulata - Annual, glabrous; leaves usually oblanceolate, typically broadest at apices, apices acute; glands 4; fruits warty, warts short; seeds reticulate. Seemingly restricted to North America, widespread. US
E. alta - Annual, glabrous; leaves usually oblanceolate, typically broadest at apices, apices acute; glands 4; fruits warty, warts long; seeds reticulate; restricted to SW United States and NW Mexico. US
E. texana - Annual, glabrous; leaves usually oblanceolate, typically broadest at apices, apices acute; glands 4; fruits smooth; seeds reticulate. Restricted to E Texas and Louisiana in the United States. US
E. helioscopia - Annual, glabrous; leaves usually obovate, broadest at apices, apices rounded or truncate; glands 4; fruits smooth. Originally from Eurasia, but introduced elsewhere. NZ US

Other species:
E. apios: link 1
E. hirsuta: link 1
E. palustris:
E. pterococca: link 1
E. valerianifolia: Fruits sparsely long pilose; link 1

Notes on E. oblongata/depauperata.

Posted on May 28, 2019 17:41 by nathantaylor nathantaylor | 0 comments | Leave a comment