Question: What is the difference between Stachyurus and Cucumis?

Context paragraphs:
Volta potential: The Volta potential (also called Volta potential difference, contact potential difference, outer potential difference, Δψ, or "delta psi") in electrochemistry, is the electrostatic potential difference between two metals (or one metal and one electrolyte) that are in contact and are in thermodynamic equilibrium.  Specifically, it is the potential difference between a point close to the surface of the first metal, and a point close to the surface of the second metal (or electrolyte).

Stachyurus: Stachyurus is the only genus in the flowering plant family Stachyuraceae, native to the Himalayas and eastern Asia.  They are deciduous shrubs or small trees with pendent racemes of 4-petalled flowers which appear on the bare branches before the leaves.  The plants have leaves with serrate margins.  Stachyuraceae contains a single genus with eight species.

Cucumis (website): Cucumis is a website where translators share their linguistic knowledge and exchange services online.  One unusual feature of Cucumis is that all translations are peer reviewed and may be edited by other Cucumis translators.  This provides for high quality translations, and often achieves a target text that is both faithful in meaning to the source text and fully idiomatic in the target language.

Phonemic contrast: Phonemic contrast refers to a minimal phonetic difference, that is, small differences in speech sounds, that makes a difference in how the sound is perceived by listeners, and can therefore lead to different mental lexical entries for words.  For example, whether a sound is voiced or unvoiced (consider /b/ and /p/ in English) matters for how a sound is perceived in many languages, such that changing this phonetic feature can yield a different word (consider "pat" and "bat" in English); see Phoneme.  Other examples in English of a phonemic contrast would be the difference between "leak" and "league;" the minimal difference of voicing between [k] and [g] does lead to the two utterances being perceived as different words.  On the other hand, an example that is not a phonemic contrast in English is the difference between [sit] and [siːt] .  In this case the minimal difference of vowel length is not a contrast in English and so those two forms would be perceived as different pronunciations of the same word "seat".

Cucumis: Cucumis is a genus of twining, tendril-bearing plants in the Cucurbitaceae family which includes the cucumber ("Cucumis sativus"), muskmelons ("Cucumis melo", including cantaloupe and honeydew), the horned melon ("Cucumis metuliferus"), and the West Indian gherkin ("Cucumis anguria").

Stachyurus praecox var. matsuzakii: Stachyurus praecox" var.  "matsuzakii (Hachijō-kibushi, ハチジョウキブシ), is a variety of "Stachyurus praecox", and is only found in Japan.  Compared to the other "Stachyurus praecox" varieties, this variety has thicker branches, longer inflorescences, and larger fruits.

Difference theory: Difference theory has roots in the studies of John Gumperz, who examined the differences in cross-cultural communication.  While difference theory deals with cross-gender communication, the male and female genders are often presented as being two separate cultures, hence the relevance of Gumperz's studies.  In her development on the difference theory Deborah Tannen in particular drew on the work of Daniel Maltz and Ruth Borker and their 1982 paper "A Cultural Approach to Male-Female Miscommunication", which itself drew on the work of Gumperz.  Mary Talbot makes reference to the term "gender-specific culture" in her critique of the difference theory, and this idea of genders being culturally separated is embodied by the 1992 publication "Men Are from Mars, Women Are from Venus".  Difference theory is often compared with dominance theory and deficit theory, and together with the more contemporary dynamic theory they make up four of the theories most widely referred to and compared in the study of language and gender.

Difference set: In combinatorics, a formula_1 difference set is a subset formula_2 of size formula_3 of a group formula_4 of order formula_5 such that every nonidentity element of formula_4 can be expressed as a product formula_7 of elements of formula_2 in exactly formula_9 ways.  A difference set formula_2 is said to be "cyclic", "abelian", "non-abelian", etc., if the group formula_4 has the corresponding property.  A difference set with formula_12 is sometimes called "planar" or "simple".  If formula_4 is an abelian group written in additive notation, the defining condition is that every nonzero element of formula_4 can be written as a "difference" of elements of formula_2 in exactly formula_9 ways.  The term "difference set" arises in this way.

Sphingomonas melonis: Sphingomonas melonis is a bacterium from the genus of Sphingomonas which has been isolated from the plant Cucumis melo var.  inodorus in Madrid in Spain.  "Sphingomonas melonis" can cause brown spots on melon fruits from the melon plant (Cucumis melo var.  inodorus).

Relative change and difference: In any quantitative science, the terms relative change and relative difference are used to compare two quantities while taking into account the "sizes" of the things being compared.  The comparison is expressed as a ratio and is a unitless number.  By multiplying these ratios by 100 they can be expressed as percentages so the terms percentage change, percent(age) difference, or relative percentage difference are also commonly used.  The distinction between "change" and "difference" depends on whether or not one of the quantities being compared is considered a "standard" or "reference" or "starting" value.  When this occurs, the term "relative change" (with respect to the reference value) is used and otherwise the term "relative difference" is preferred.  Relative difference is often used as a quantitative indicator of quality assurance and quality control for repeated measurements where the outcomes are expected to be the same.  A special case of percent change (relative change expressed as a percentage) called "percent error" occurs in measuring situations where the reference value is the accepted or actual value (perhaps theoretically determined) and the value being compared to it is experimentally determined (by measurement).

Supporting paragraphs: Stachyurus Cucumis
Answer: Stachyuraceae contains a single genus with eight species.