Bentham and Hooker’s system of classification was published as a three volumed work in Latin with the title Genera Plantarum. About two third of the work was done by Bentham and the rest by Hooker. It was a tremendous task required a period of 25 years of concentrated effort.
The Genera Plantarum has taken into consideration of all the seeded plants including Gymnosperm. Total number of species worked out by Bentham and Hooker was 97205 species coming under 202 families.
Bentham and Hooker divided the Angiospermae into two classes: Dicotyledons and Monocotyledons and in between this they have placed Gymnosperms. Dicotyledon is again divided into three subclasses. They are Polypetalae,
Gamopetale and Monochlamydeae. These sub classes are again divided into series. Series is again divided into order or cohort and order into family.Merits
1. One of the most valuable contribution of this work is the description of the taxa at all levels. Description are accurate and easy to identify plant species up to family level.
2. Because the description were based on direct observation by the authors they become models of accuracy.
3. This system placed order Ranales placed at the beginning of the system is very reasonable.
4. The placement of dicots before monocots is also accepted by all the modern taxonomists.
1. Gymnosperms are most primitive than angiosperms and placing gymnosperms in between dicots and monocots is a serious error.
2. The introduction of monochlamydeae is another drawback . Since this group contains advanced and primitive forms.
3. Among the monocot Orchidaceae is placed in the beginning with all it’s advanced characters.
4. The subdivision of the monocot is based on the position of ovary and characters of perianth. This may resulted in the anomalous situation for many families.