The genus Euphrasia L., is revised from Pakistan and its adjoining areas. The revision is based on the data obtained from different disciplines of botany, which also includes the systematic treatment of the genus. In all 31 taxa are recognized, including 5 new species and 3 new records from this region. Most of the names whether accepted or synonyms are typified. An artificial key is prepared, accompanied by full description and illustrations of 29 taxa recognized. Taxonomic notes are also given at the end of each taxon.
Seed morphology of 30 species, with the help of light and scanning electron microscopy has been studied. Differences in surface patterns including the relative thickness of the radial walls (transverse and longitudinal, depth, size and shape of the areolae) are taxonomically significant, and two primary groups are recognized viz. (1) deep areolate type (2) shallow areolate type. Other characters such as the size, general shape and colour of the seeds provide little assistance in the taxonomy of the genus.
Palynologically 27 species were investigated. Three groups are recognized on the basis of the differences in the sculpturing pattern, viz. (1) coarsely retipilate (2) finely retipilate (3) rugulate-retipilate, with granulated muri. Further subdivision of these basic groups is done on the basis of the differences in the colpus membrane sculpturing, which may be granulate or granulate-retipilate; but none of them is exclusive for a particular group. Quantitative characters such as the equatorial length and breadth, polar diameter, colpus length and breadth, size of the apocolpium and the mesocolpium and the exine thickness provide additional support regarding specific delimitation.
Phenolic constituents of 26 species of the genus were ar1alyzed. On the basis of the presence and absence of various compounds and the frequency of occurrence of a particular compound, various Euphrasia L., species were delimited. However, Azaleaten 3-galactoside and o-coumaric acid are universally present in all the taxa analyzed and perhaps are characteristics of the genus.
Anatomical characters of the stem, root and the seed were examined. Three anatomical patterns, each specific to stem, root and the seed are recognized. The histological characters seemed to be useful in clarifying the taxonomy of the genus. A new term regarding the anatomical characters of seeds viz "Euphrazoid" type is coined in which the hypodermis is 2-3 layered, whose cells are diametrically or tangentially elongated and reticulate thickenings are present in the hypodermal layer. The: epidermis is uniformly radially elongated. Transverse section of the stem shows a single layered epidermis, 2.3 layered cortex, single layered endodermis and the pericycle, no vascular bundles but well developed vessels and fibres cells. Transverse section of the root shows no epidermis, ruptured cortex, endodermis and the pericycle, however vessels and fibre cells are present. On the basis of the distribution of vessel cells 5 broad groups are recognized.
The data thus obtained is subjected to the numerical analysis. The cumulative data is subjected for clustering analysis and ordination. Dendrograms and biplots were produced indicating groupings and relationships among different species.