Almost nothing is known about this German horticulturist.
No copyright (public domain)
This is a book of historical value and probably the starting point of the German cactus literature. It is hard to read because it was printed using gothic (fraktur) letters. There is no picture.
The OCR 3) is not reliable with gothic letters, and the interpreted text is often a meaningless series of letters. Thus, searching text is risky. Fortunately, Förster used latin letters for many latin names. The text is easier to read than the reprint of the '80s.
No copyright (public domain)
This is the second edition produced by Theodor Rümpler. Besides many additions, there are 140 plates, and it is written using standard Latin letters.
Two pdf files containing both the original and an “interpreted text” can be downloaded from Missouri Botanical Garden Library.4):