Franklin W. Dixon

That passage does not appear in the 1928 edition, which has no references to botany as such. 

In chapter 2 of the later edition, we find: 

‘“Common sense,” Chet intoned. “You see, we live in a dangerous world, never knowing where our next meal may come from. So, I figure to learn a little botany in case I’m ever marooned on a jungle island or too far from a hot-​dog stand. In other words, herbivorous survival.”’