Question: What characteristic does the Quince and the Isoplexis share? 

Context paragraphs:
Worker cooperative: A worker cooperative is a cooperative that is owned and self-managed by its workers.  This control may be exercised in a number of ways.  A cooperative enterprise may mean a firm where every worker-owner participates in decision-making in a democratic fashion, or it may refer to one in which management is elected by every worker-owner, and it can refer to a situation in which managers are considered, and treated as, workers of the firm.  In traditional forms of worker cooperative, all shares are held by the workforce with no outside or consumer owners, and each member has one voting share.  In practice, control by worker-owners may be exercised through individual, collective, or majority ownership by the workforce; or the retention of individual, collective, or majority voting rights (exercised on a one-member one-vote basis).  A worker cooperative, therefore, has the characteristic that each of its workers own one share, and the all shares are owned by the workers.  The International organisation representing worker cooperatives is CICOPA.  CICOPA has two regional organisations: CECOP- CICOPA Europe and CICOPA Americas.

Live oak: Live oak or evergreen oak is a general term for a number of unrelated oaks in several different sections of the genus "Quercus" that share the characteristic of evergreen foliage.

Indigenous peoples: Indigenous peoples, also known as first peoples, aboriginal peoples, native peoples, or autochthonous peoples, are ethnic groups who are descended from and identify with the original inhabitants of a given region, in contrast to groups that have settled, occupied or colonized the area more recently.  Groups are usually described as indigenous when they maintain traditions or other aspects of an early culture that is associated with a given region.  Not all indigenous peoples share this characteristic, sometimes having adopted substantial elements of a colonising culture, such as dress, religion or language.  Indigenous peoples may be settled in a given locale/region or exhibit a nomadic lifestyle across a large territory, but they are generally historically associated with a specific territory on which they depend.  Indigenous societies are found in every inhabited climate zone and continent of the world.

Immutable characteristic: An immutable characteristic is any sort of physical attribute which is perceived as being unchangeable, entrenched and innate.  The term is often used to describe segments of the population which share such attributes and are contrasted from others by those attributes, and is used in human rights law to classify protected groups of people who should be protected from civil or criminal actions which are directed against those immutable characteristics.

Volkssturmgewehr: The Volkssturmgewehr ("People's Assault Rifle") is the name of several rifle designs developed by Nazi Germany during the last months of World War II.  They share the common characteristic of being greatly simplified as an attempt to cope with severe lack of resources and industrial capacity in Germany during the final period of the war.

Art Deco in Durban: Durban, South Africa has a notable number of buildings built in the Art Deco style popularised in the USA in the 1930s.  Durban-style Art Deco buildings share the characteristic bold colours, geometric shapes and glamorous ornamentals of the global style, while incorporating local narratives and motifs.

Histiocytosis: In medicine, histiocytosis refers to an excessive number of histiocytes, ("tissue macrophages"), and is typically used to refer to a group of rare diseases which share this as a characteristic.  Occasionally and confusingly, the term "histiocytosis" is sometimes used to refer to individual diseases.

Isoplexis: Isoplexis is a section of 4 species of flowering plants within the genus "Digitalis" in the plantain family Plantaginaceae.  The species of section Isoplexis differ from other plants in the genus "Digitalis" in that their monosymmetric (sometimes called zygomorphic) flowers have a distinctive large upper lip rather than large lower lip and the species are endemic to the Canary Islands (the species "D. canariensis", "D. chalcantha", and "D. isabelliana") and Madeira ("D. sceptrum").

Cohort study: A cohort study is a particular form of longitudinal study (panel study) that sample a cohort (a group of people who share a defining characteristic, typically who experienced a common event in a selected period, such as birth or graduation), performing a cross-section at intervals through time.  A cohort study is a panel study, but a panel study is not always a cohort study as individuals in a panel study do not always share a common characteristic.

Quince: The quince ( ; "Cydonia oblonga") is the sole member of the genus Cydonia in the family Rosaceae (which also contains apples and pears, among other fruits).  It is a small deciduous tree that bears a pome fruit, similar in appearance to a pear, and bright golden-yellow when mature.  Throughout history the cooked fruit has been used as food, but the tree is also grown for its attractive pale pink blossoms and other ornamental qualities.

Supporting paragraphs: Quince Isoplexis
Answer: flowering plants