One hundred thirty-six years passed from the time Plumier first introduced plants of what came to be known as Philodendron to European scientists in 1693 and the first modern circumscription of the genus by Schott in 1829. During this interim a number of workers, including Carl Linnaeus, worked with generic concepts and came to realize that not all aroids belonged in the same genus. Arum came to be used only for the European plants it now represents and Arisaema,Dracunculus, and Colocasia were also separated by the early eighteenth century (Hermann, 1698; Tournefort, 1700). By the fifth edition of `Genera Plantarum' Linnaeus (1754) had recognized also Calla, Dracontium, and Pothos as well as Orontium, Pistia, and Acorus, although not recognizing the last three as related to Arum.

By the middle of the eighteenth century the exploration of the neotropics was well under way. The introduction of so many new plants from the New World tropics, including many Philodendron species, made it clear that further separation was needed. Because of the uncritical acceptance of many aberrant elements into Arum during the course of the eighteenth century a number of taxa now recognized as Caladium, Philodendron, and Syngonium were incorporated into Arum. Ventenant (1800) solved part of the problem by recognizing Caladium, but Willdenow (1805) erred in transferring into Caladium four of Jacquin's West Indian Philodendron species (all considered Arum at the time).

Even by the time of the 16th edition of Species Plantarum Sprengel (1826) still did not recognize Philodendron but had increased the number to 12, adding Ambrosina, Arisarum, Caladium, Gymnostachys, and Zantedeschia.

Resolution of many of the remaining generic problems with the Araceae awaited Austrian botanist Heinrich Wilhelm Schott who was the first to devote himself almost exclusively to the taxonomy of the Araceae (Nicolson, 1960). Schott was uniquely qualified in this regard, having spent four years in Brazil collecting plants and with access to the large collection of living plants at the Imperial Gardens of the Hapsburg's at Schönbrun Palace in Vienna where he worked as the director. These included his own Brazilian collections as well as those of N. J. Jacquin from the Caribbean. In 1829 Schott described the genus Philodendron (published as Philodendrum) in one of his first publications after returning from Brazil in 1821. The first species placed in the genus, P. ligulatum, originally described as Arum ligulatum L., is a member of P. subg. Pteromischum. In 1832 Schott published a preliminary classification of the Araceae in a work entitled `Meletemata Botanica', which included many plant families and was done in conjunction with his colleague S. Endlicher. In this work he recognized 39 genera of Araceae including Philodendron and some other by now well known species-rich genera such as Anthurium, Syngonium, Dieffenbachia, Aglaonema and Spathiphyllum. In this work he also published the first infrageneric system of classification for Philodendron although it contained only three groups that are still recognized today. Though Schott subsequently continued to work on his circumscription of the genera and species of the Araceae for the remainder of his career, he did not publish any major revisions of Araceae for 24 years.

Endlicher (1837), publishing alone but with the obvious assistance of Schott (Mayo, 1990), produced a revision of Philodendron which differed from the `Meletemata' account by Schott only in having a more complete generic description, including vegetative details which were presented for the first time.

Shortly after Endlicher's revision, K. S. Kunth (1841) published in his `Enumeratio Plantarum...' the first species-level revision of Philodendron. This revision included new species and new combinations and for the first time included species of the genus which would be later recognized as members of P. subg. Pteromischum.

It was not until Schott's publication of a work entitled `Synopsis aroidearum' (Schott, 1856) that a fully developed infrageneric system of classification was realized. This was Schott's first species-level revision of the genus and the `Synopsis' divided the genus into 22 `greges' grouped in 7 unnamed categories arranged in increasing order of leaf base shape (Mayo, 1990). A total of 99 species (including 12 members of P. subg. Pteromischum which is recognized here for the first time), and three species of P. subg. Meconostigma were included (two of them reported as members of Sphincterostigma). It was also the first time that a true Central American member of P. subg. Philodendron was published. This was P.hederaceum (Jacq.) Schott, published originally as Arum hederaceum Jacq.

Schott's final classification of Philodendron was published four years later in the `Prodromus Systematis Aroidearum' (1860), a more rigorous work that came to be his last comprehensive self- published work since he died at the age of 71 in 1865. This revision included 110 genera, almost all of which are still recognized as genera or subgenera. The fact that his work has stood the test of time is a testimony to the serious nature of the research he had done in Vienna during his long period of seeming inactivity.

Schott's treatment of Philodendron in the Prodromus differs from his revision in the `Synopsis' in having more complete descriptions, using more inflorescence characters, in having six rather than seven unnamed categories of leaf shape to group the 'greges' and in beginning to make use of the cataphyll (prophyll in the strictest modern sense) as a character. Schott used the term "subopposite stipule" for the feature which came to be known as the cataphyll in Engler's usage. This feature has proven to be one of the best and most reliable characters for the genus. For a detailed listing of the key characters for Philodendron used in Schott's Prodromus revision refer to Mayo (1990, p. 50).

The Prodromus treatment included 135 species (up from 99 in the `Synopsis') of Philodendron included in the same `greges'. Twenty species of the total were members of P. sect. Pteromischum Schott and 6 species are now placed in P. sect. Meconostigma (Schott) Engl. (3 in grex Meconostigma and 3 in grex Sphincterostigma). Thus Schott included 110 names of P. sect. Philodendron. Taking synonymy into account, only 76 species of P. sect. Philodendron were included in this 1860 revision. Only 18 names pertained to Central America. Of these, only 8 are accepted members of P. sect. Pteromischum.

The species included by Schott (1860) in each grex of the Prodromus for Central American are listed below:

Grex Baursia Reichb.:

P. wendlandii Schott
Grex Pteromischum Schott:
P. aurantiifolium Schott,
P. seguine Schott,
P. inaequilaterum Liebm.
Grex Canniphyllum Schott:
(no species represented)
Grex Glossophyllum Schott:
(no species represented)
Grex Solenosterigma Klotzsch:
P. oxycardium Schott,
P.micans Klotzsch,
P. scandens K. Koch & Sello = (P. hederaceum)
Grex Psoropodium Schott:
P. tenue K. Koch,
P. gracile Schott
Grex Achyropodium Schott:
P. verrucosum Mathieu
Grex Platypodium Schott:
P. pterotum K. Koch,
P.fragrantissimum (Hook.) Kunth
Grex Cardiophylacium Schott:
P. brevispathum Schott,
P.hederaceum Schott (= P. jacquinii Schott)
Grex Belocardium Schott:
P. hoffmannii Schott, P. advena,
P. acrocardium Schott
Grex Cardiobellium Schott:
(no species represented)
Grex Meconostigma Schott:
(no species represented)
Grex Eubelium Schott:
(no species represented)
Grex Macrolonchium Schott:
(no species represented)
Grex Macrobelium Schott:
P. daemonum Liebm. = P.sagittifolium Liebm.,
P. sagittifolium Schott,
P. tanyphyllum Schott = P. sagittifolium Liebm.
Grex Imbéa:
(no species represented)
Grex Oligophlebium Poepp.:
(no species represented)
Grex Doratophyllum Schott:
(no species represented)
Grex Schizophyllum Schott:
(no species represented)
Grex Tritomophyllum Schott:
P. tripartitum (Jacq.) Schott,
P. dagilla Schott = P. tripartitum (Jacq.) Schott,
P. anisotomum Schott
Grex Polytomium Schott:
P. subincisum Schott,
P. impolitumSchott = P. radiatum Schott,
P. polytomum Schott = P.radiatum Schott,
P. warszewiczii
Grex Sphincterostigma Schott:
(no species represented)

In all, only 18 of the 135 species of Philodendron were included in this 1860 revision for Central America, 27 of which were members of P. subg. Philodendron. These included one species, P. ligulatum, which Schott had inadvertently placed in his grex Pteromischum. This total number is further reduced by three since P. acrocardium, P. hoffmannii, P. oxycardium, and P. micans have been reduced to synoyms, subspecies and or forms of P. hederaceum and P. gracile is a synonym of P. tenue. In addition, P. daemonum and P. tanyphyllum were synonyms of P. sagittifolium and P. impolitum and P. polytomum are synonyms of P. radiatum. Thus Schott was dealing with only 11 of the 96 Central American species (only 14.6% of the currently known flora.