Morphology

Achlorophyllous plant Plants lacking the green pigment chlorophyll found in all photosynthetic plant cells.   Armed plant Plants that produce various types of sharply-pointed structures such as thorns, spines, prickles, or specialized hairs.  These structures can be produced on any part of the plant, including fruits, cones, stems, leaves, inflorescences, etc.  Due to the difficulty and ambiguity of this field, it is not yet fully populated.   I have taken the liberty to include members of the Urticaceae, since many of its species have painfully sharp specialized trichombs, but have not done so with other members of the Boraginaceae, since they aregenerally not as mechanically injurious.  I have also been somewhat selective by including certain members of the genus Galium, i.e., those species with mostly sharply-spined leaf apices, but have ignored other members of the genus with only specialized stem hairs.  In a few cases, I have also included species of genera (Euonymus, Planera) with fleshy protuberances on their fruits.  Any comments would be welcomed.   Bulb plant Plants having bulbs; a bulb is a short stem axis surrounded by thick, fleshy, modified leaves, producing a broadly ovoid, underground storage organ.  The whole bulb is equivalent to a "shoot" - a leafy stem. Bulbs, in this strict definition (which is used here), are restricted to two monocot families (Iridaceae and Liliaceae) and one dicot family (Oxalidaceae).  The bulbous habit has arisen independently  several times even within a single section of Oxalis.  Plants of some species arise from a "bulbous-thickened base" (e.g. Xyris isoetifolia, Poa bulbosa, Luzula bulbosa), where the thickening is produced from the leaf bases of functional, above-ground leaves.   Bulblets, which are miniature bulbs usually significant in asexual reproduction, are characteristic of some genera, e.g., Luzula (Juncaceae), Bolandra and Suksdorfia (Saxifragaceae), Dicentra (Fumariaceae),Oxalis (Oxalidaceae), Calochortus (Liliaceae).  They may be produced in various places, such as rhizome tips or the axils of cauline leaves ("bulbels") or bulb scale leaves ("bubils").  Production of bulblets as a biological attribute is not included in this version of the Synthesis.   Some working definitions of "bulb," especially in horticultural contexts, are broadened to include various other types of underground storage organs, such as swollen stems (corms, rhizomes, tubers) and swollen roots ("tuberous roots").  Various descriptions and epithets referring to bulbs technically refer to other types of structures (e.g., Cardamine bulbosa - tuber, Cicuta bulbifera - tuberous roots, Dioscorea bulbifera - tuber, Erigenia bulbosa - tuber, Ranunculus bulbosa - corm).   Corms also are swollen, underground storage organs equivalent to a "shoot," but the stem (rather than the leaves) is swollen and bears few to numerous, thin, scale-like leaves that do not provide storage capacity.  Corms also are relatively common among monocots but are produced within only a few genera of dicot families (e.g., Anemone, Eranthis, and Ranunculus - Ranunculaceae; Cyclamen - Primulaceae; Begonia - Begoniaceae; Achimenes, Gesneria and Gloxinia - Gesneriaceae; Corydalis - Fumariaceae).  Corms with few, small leaves may approach tubers in their technical definition.  The "scaly bulbous base" of some species of Oxalis, where the leaves are dry and scaly relative to a typical monocot bulb, might be considered somewhat intermediate between a bulb and corm.   Geophyte Perennial plants that bear their overwintering buds below the surface of the soil on bulbs, corms, tubers, or in some cases, rhizomes.   Leaf   Evergreen plant Plants with foliage that remains green and functional through more than a single growing season.  For the purpose of the Synthesis, I have populated only the evergreen trees, shrubs, subshrubs, and lianas of continental North America.  Since this is an extremely variable field, especially for these groups in the southern reaches of the continent, it remains somewhat incomplete.  Any assistance would be appreciated.   Tendrils Usually slender, forking, or simple modified leaves or portions of leaves that aid in supporting plant stems that are vining or twining.  Two forms are distinguished in the Synthesis:   Tendrils with disks Tendrils that terminate in small, plate-like structures, which appear as thin disks.   Tendrils without disks Usually slender, forking, or simple modified leaves or portions of leaves that aid in supporting plant stems that are vining or twining.   Stem texture   Herbaceous plant Non-woody plants lacking a persistent, woody, above-ground stem.   Semi-woody plant Plants producing a suffrutescent or obscurely ligneous stem with limited woody tissue.   Woody plant Plants producing a ligneous stem, primarily resulting from secondary xylem.