Ageratum ( ), (whiteweed in the USA), is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native to the United States.
Scientists are unsure or not in firm agreement as to the exact number of species in the genus Ageratum.
The context says there are 40-60 species in the genus Ageratum. Per common knowledge, Scientists are primarily responsible for the classification and enumeration of species. Because 40-60 is an indeterminate number (as it is a range of numbers), the consensus among scientist (the counters) is that there are an indeterminate number of species in the genus Ageratum.