Morphological and Cytological Studies in the Genus Lantana L.

1. Chromosome numbers in L. wightiana and L. montevidensis have been recorded for the first time. These plants have a basic number of n = 12 which is the same for all the species studied so far except L. camara.

2. Of the plants studied, polyploid races were observed in L. camara var. mutabilis only. In this variety there is no correlation between flower colour and chromosome number. In nature tetraploids and to a lesser extent triploids are predominant.

3. Stomata are confined to lower epidermis only. The number of stomata per square millimetre varies at the species level, but is more or less constant in all the three varieties and polyploid races of L. camara. The diploid forms of all the three varieties of Lantana camara have smaller stomata when compared to the higher polyploids.

4. In all the plants studied, 4-8 microspores were found due to laggards forming small micro-nuclei.

5. In spite of a regular meiosis in L. camara var. nivea and Lantana montevidensis pollen grains were found to be completely sterile. Conversely, in spite of irregular meiosis in some of the triploids of var. mutabilis, pollen fertility was very high. In var. crocea partial sterility prevails, though meiosis is normal. Sterility in Lantana is not merely due to chromosomal aberrations but is also gene controlled.

6. Even completely male sterile species produced viable seeds. Preliminary studies seem to indicate the prevalence of apomixis in this genus.