Here's a huge HT to the Agricultural Biodiversity Blog for alerting us to the over 14 million images obtained by scanning books in the public domain, books on which the intellectual property rights have expired, a date that varies quite a bit from place to place, generally 70 years after the death of the author in the USA. At any rate, these are available at the Internet Archive but just browsing could take quite awhile. Search the commons on botany or plants and you'll get to see all manner of great old line drawings and illustrations, some of excellent detail and accuracy especially given their age. Here's an Epiphyllum, an orchid cactus, from Paxton's Magazine of Botany (1841); it caught TPP's attention because mine started flowering today, about three weeks after being brought inside for the winter.
Sixty-four years later: How Watson and Crick did it
21 hours ago in The Curious Wavefunction