The first comprehensive exposition of the relationship between genetics and natural selection in plants, and the most imporant book on plant evolution published during the 20th century.  Stebbins combined genetics and natural selection to describe plant speciation. His work was one of the main publications that formed the core of the modern evolutionary synthesis and still provides the conceptual framework for research in plant evolutionary biology.

"According to Ernst Mayr, 'Few later works dealing with the evolutionary systematics of plants have not been very deeply affected by Stebbins' work"^[2]....

"The 643-page book cites more than 1,250 references and was the longest of the four books associated with the modern evolutionary synthesis. The other key works of the modern evolutionary synthesis, whose publication also followed their authors' Jesup lectures, are Theodosius Dobzhansky's Genetics and the Origin of Species, Ernst Mayr's Systematics and the Origin of Species and George Gaylord Simpson's Tempo and Mode in Evolution. The great significance of Variation and Evolution in Plants is that it effectively killed any serious belief in alternative mechanisms of evolution for plants, such as Lamarckian evolution or soft inheritance, which were still upheld by some botanists.^[2] Stebbins book Flowering Plants: Evolution Above the Species Level was published in 1974 and was based on the Prather Lectures which he gave at Harvard. It is considered as an update to Variation and Evolution." (Wikipedia article on Variation and Evolution in Plants, accessed 02-2017).