At 93, botanist Bill Weber is one of the oldest professors at University of Colorado -Boulder. Back in 1953, he wrote the first field guide to plants in Colorado. The fourth edition of "Colorado Flora" is just out. What started as just a survey of front range plants is now two books: one for the Western slope, and another for the eastern part of the state. Weber, who also started the herbarium at CU, speaks with Colorado Public Radio's Ryan Warner.