In chemistry, pi bonds (π bonds) are covalent chemical bonds where two lobes of an orbital on one atom overlap two lobes of an orbital on another atom.
 Each of these atomic orbitals is zero at a shared nodal plane, passing through the two bonded nuclei.
 The same plane is also a nodal plane for the molecular orbital of the pi bond.
Lithophragma is a genus of flowering plants containing about nine species native to western North America.
 These plants are known generally as woodland stars.
 The petals of the flowers are usually bright white with deep, long lobes or teeth.
 Each petal may look like three to five petals, when at closer inspection the lobes fuse into a single petal at its base.
 Most species reproduce via bulblets instead of seeds.
 "L. maximum" is a federally listed endangered species.
Downingia ornatissima is a species of flowering plant in the bellflower family known by the common name folded calicoflower.
 This showy wildflower is endemic to California, where it is a resident of vernal pools and other wet places in the Central Valley.
 This annual grows an erect, branching stem with usually one tubular flower at the top of each branch.
 The flower has an upper lip made up of two narrow, pointed lobes in shades of light purple, and a lower lip made up of three lobes fused into one surface, which is the same color as the upper lip and has a central field of white with two prominent yellow projections.
 The flower is similar to those of other downingias, except it is lightly crinkled, with the upper lobes often curled back and the edges of the lower lobes uneven.
 The dark blue anther just emerges from where it is tucked between the upper lobes.
Clarkia xantiana is a species of flowering plant in the evening primrose family known by the common name gunsight clarkia.
 It is endemic to California, where it is known from the southern Sierra Nevada and its foothills and the adjacent Transverse Ranges.
 This is an erect annual herb with linear to lance-shaped leaves each up to 6 centimeters long.
 The inflorescence produces opening flowers and closed buds.
 The sepals stay fused as the petals bloom from one side.
 Each petal is up to 2 centimeters long and generally light to medium purple in color, sometimes with a dark, ringed spot on the petals of the upper whorl.
 The petal has a narrow claw and a wider blade which has two lobes at the tip with a small tooth between.
Silene menziesii is a species of flowering plant in the pink family known by the common names Menzies' campion and Menzies' catchfly.
 It is native to western North America from Alaska through the western half of Canada to the southwestern United States.
 It can be found in many types of habitat and it is quite common in much of its range.
 It is variable in morphology and there are a number of varied subtaxa.
 In general, it is a perennial herb growing from a caudex, appearing matlike, decumbent, or erect, with stems a few centimeters to over half a meter long.
 It is usually hairy in texture, with upper parts bearing sticky glandular hairs.
 The leaves are lance-shaped, oppositely arranged in pairs, and a few centimeters in length, upper leaves usually smaller than lower.
 Flowers may occur in a cyme at the top of the stem, or in leaf axils, or both.
 Each is encapsulated in a hairy, veined calyx of fused sepals.
 The petals are white with two lobes at the tips.
 The plant is dioecious with male and female plants producing different flowers.
 The male and female flower types look the same externally; the stamens are reduced in female plants and the stigmas are reduced in the male.
Mohavea breviflora is a species of flowering plant in the plantain family known by the common names golden desert-snapdragon and lesser mohavea.
 It is native to the southwestern United States, including the Mojave Desert and surrounding areas.
 It is a hairy annual herb growing erect to a maximum height near 20 centimeters.
 The alternately arranged leaves are lance-shaped.
 Flowers occur in the leaf axils.
 They are about 2 centimeters wide and divided into an upper lip with two lobes and a swollen lower lip with three.
 The flower is yellow with scattered red speckles.
Westringia is a genus of Australian shrubs.
 As with other members of the mint family their upper petal (or lip) is divided into two lobes.
 There are four stamens - the upper two are fertile while the lower two are reduced to staminodes.
 The leaves are in whorls of 3 or 4.
Cardamine pensylvanica is a species of "Cardamine" known by the common name Pennsylvania bittercress.
 It is native to most of Canada and the United States from coast to coast.
 It is generally found in moist to wet areas, such as the mud on riverbanks.
 It is a biennial herb producing one or more erect or leaning, branching stems which are purple to green in color and grow 10 - tall.
 The leaves are hairless and divided into several rounded to oval lobes, each of which has one or two lobes, with the exception of the large terminal leaflet at the tip, which generally has three.
 Most of the leaves are located along the stem and there is no basal rosette.
 The inflorescence comprises many flowers, each with four white petals a few millimeters long.
 The fruit is a slender silique 2 - long.
Hemigenia is a genus of flowering plants in the mint family, Lamiaceae and is endemic to Australia where most species occur in Western Australia, although some are also found in New South Wales and Queensland.
 Plants in this genus are shrubs or bushes with simple leaves and tube-shaped flowers with the petals forming two "lips" - the upper one with two lobes and the lower one with three.
Ammobium is genus of perennial Asteraceae species described as a genus in 1824.

Question: Which plants upper petal is divided into two lobes, Ammobium or Westringia?
Answer: Westringia