| Infrageneric Classification of Salix (Salicaceae) in the New World | 1997/01/01 | English | 119 |
| Revision of Crataegus Sect. Crataegus and Nothosect. Crataeguineae (Rosaceae-Maloideae) in the Old World | 1992/01/01 | English | 88 |
| Malvaceae of Mexico | 1988/01/01 | English | 86 |
| Wild Potatoes (Solanum section Petota; Solanaceae) of North and Central America | 2004/01/01 | English | 73 |
| The Genus Salix (Salicaceae) in the Southeastern United States | 1986/01/01 | English | 66 |
| Monograph of Schisandra (Schisandraceae) | 2000/01/01 | English | 66 |
| Monograph of Phoradendron (Viscaceae) | 2003/01/01 | English | 55 |
| Plagiochila (Hepaticae, Plagiochilaceae) in China | 2001/01/01 | English | 51 |
| Monograph of Kadsura (Schisandraceae) | 1998/01/01 | English | 49 |
| Systematics of Oenothera Section Oenothera Subsection Oenothera (Onagraceae) | 1997/01/01 | English | 45 |
| Revision of Passiflora Subgenus Decaloba Section Pseudodysosmia (Passifloraceae) | 1994/01/01 | English | 44 |
| A Monograph of Nymphaea Subgenus Hydrocallis (Nymphaeaceae) | 1987/01/01 | English | 44 |
| Systematics of the New World Species of Marsilea (Marsileaceae) | 1986/01/01 | English | 43 |
| Revision of Sorbus Subgenera Aria and Torminaria (Rosaceae-Maloideae) | 2004/01/01 | English | 42 |
| The Systematics of Acmella (Asteraceae-Heliantheae) | 1985/01/01 | English | 40 |
| Monograph of Podostemum (Podostemaceae) | 2004/01/01 | English | 39 |
| Azpeitia (Bacillariophyceae): Related Genera and Promorphology | 1986/01/01 | English | 39 |
| Revision of the Mexican Species of Cyperus (Cyperaceae) | 1994/01/01 | English | 37 |
| Monograph of Leucaena (Leguminosae-Mimosoideae) | 1998/01/01 | English | 36 |
| Monograph of Andira (Leguminosae-Papilionoideae) | 2003/01/01 | English | 36 |
| Monograph of Mecranium (Melastomataceae-Miconieae) | 1993/01/01 | English | 34 |
| Revision of Tristerix (Loranthaceae) | 1988/01/01 | English | 33 |
| Revision of Palicourea (Rubiaceae) in Mexico and Central America | 1989/01/01 | English | 31 |
| Revision of Cymbopetalum and Porcelia (Annonaceae) | 1993/01/01 | English | 31 |
| Monograph of Stigmaphyllon (Malpighiaceae) | 1997/01/01 | English | 31 |
| Morphology and Systematics of Paepalanthus Subgenus Xeractis (Eriocaulaceae) | 1988/01/01 | English | 29 |
| Monograph of Pictetia (Leguminosae-Papilionoideae) and Review of the Aeschynomeneae | 1999/01/01 | English | 29 |
| Monograph of Desmanthus (Leguminosae-Mimosoideae) | 1993/01/01 | English | 26 |
| Revision of Cuphea Section Heterodon (Lythraceae) | 1988/01/01 | English | 25 |
| Systematics of Chusquea Section Swallenochloa, Section Verticillatae, Section Serpentes, and Section Longifoliae (Poaceae-Bambusoideae) | 1989/01/01 | English | 24 |