The orders are thus based on the form of the fruit; the genera in the _Synopsis_ number 41. Large genera such as _Lecanora_ with 132 species are divided into sections, many of which have in turn been established as genera, by S. F. Gray in 1821, and later by other systematists. The _Synopsis_ was the text-book adopted by succeeding botanists for some 40 years with slight alterations in the arrangement of classes, genera, etc. Wallroth[1023] and Meyer[1024] followed with their studies on the lichen thallus, and Wallroth’s division into “Homoiomerous” and “Heteromerous” was accepted as a useful guide in the maze of forms, representing as it did a great natural distinction. _c._ SCHAERER. This valiant lichenologist worked continuously during the first half of the nineteenth century, but with very partial use of the microscope. His last publication in 1850, an _Enumeration of Swiss Lichens_, was the final declaration of the older school that relied on field characters. His classification is as follows: Class I. Lichenes Discoidei, with ten orders from Usneacei to Graphidei; fruits open. Class II. Lichenes Capitati, with three orders: Calicioidei, Sphaerophorei and Cladoniacei; fruits stalked. Class III. Lichenes Verrucarioidei, with three orders: Verrucarii, Pertusarii and Endocarpei: fruits closed. An “Appendix” contains descriptions of Crustacei and Fruticulosi, all sterile forms, except _Coniocarpon_ and _Arthonia_, which seem out of place, and finally a “Corollarium” of gelatinous lichens all classified under one genus _Collema_. _d._ MASSALONGO AND KOERBER. As a result of their microscopic studies, these two workers proposed many changes based on fruit and spore characters, and Koerber in the _Systema Lichenum Germaniae_ (1855) gave expression to these views in his classification. He also made use of Wallroth’s distinctions of “homoiomerous” and “heteromerous,” thus dividing lichens at the outset into those mostly with blue-green and those with bright-green gonidia. The following is the main outline of Koerber’s classification: Series I. Lichenes Heteromerici. Order I. Lich. Thamnoblasti (fruticose). Order II. Lich. Phylloblasti (foliose). Order III. Lich. Kryoblasti (crustaceous). Series II. Lichenes Homoeomerici. Order IV. Lich. Gelatinosi. Order V. Lich. Byssacei. With the exception of Order V all are subdivided into two sections, “gymnocarpi” with open fruits and “angiocarpi” with closed fruits, a distinction that had long been recognized both in lichens and in fungi.