GROUP A: Leaves simple, under 4.5 mm across, usually narrowly linear, needlelike, awllike, or scalelike.
KEY TO GENERA
1. Stems jointed, succulent, green; leaves small .................................. 2
2. Stems terete, essentially evenly columnar, 2.5-3(4) mm across; leaves opposite, persistent .......................... Sarcocornia
2. Stems flattened or rarely unevenly columnar and much broader; leaves alternate, soon falling ............................. Opuntia
1. Stems rarely jointed, not succulent, year 1 stems green or otherwise; leaves short to long, at least some persistent throughout growing season .......... 3
3. Leaves whorled or opposite ....................................... 4
4. Leaves mostly or all whorled ...................................5
5. Leaf blade 1.5-5 mm, revolute, apparent margin with conspicuous long gland-tipped hairs ........................... Erica
5. Leaf blade 1.5-25 mm, revolute or flat to concave, apparent margin lacking gland-tipped hairs.................................... 6
6. Leaf blade linear, almost tubular, margin revolute ............................................................... Ceratiola
6. Leaf blade lanceolate to elliptic, flat ....... Lechea
4. Leaves opposite, rarely some whorled ................................. 7
7. Leaf blade 1-3 mm, scalelike or lance-oblong ................ 8
8. Year 1 stems succulent, over 2 mm across; leaf blade a sesssile fleshy scale, those of a pair fused to each other ......................... Sarcocornia
8. Year 1 stems woody, 2 mm across or less; leaf blade lance-oblong or consisting of firm scales, those of a pair not fused to each other ................................................................ 9
9. Leaves consisting of firm scales ............... Juniperus
9. Leaves lance-oblong, not scalelike .......... Calluna
7. Leaf blade mostly over 4 mm and usually linear-subulate to elongate or oblanceolate; if less than 4 mm then oblong to oblong-ovate, elliptic or slightly obovate or spatulate .................... 10
10. Basal half of petioles at mid-twig essentially parallel with twig and jointed with it at ca 90 ° ...................... Leiophyllum
10. Petioles absent or, if present, basal half on mid-twig leaves at an angle with twig and jointed with it less than 90 ° ...........11
11. Leaf blade with (3)4-5(8) teeth on apical half of each edge; stipules present, soon brown to marooon, 0.4-0.5 mm, linear, usually falling and leaving a short linear scar beside edges of leaf scar ................................. Pachistema
11. Leaf blade entire or with 1-3 teeth to 0.15 mm; stipules and their scars absent, a ridge sometimes present connecting edges of opposing leaf scars ................................ 12
12. Leaf blade without glands on either surface, but sometimes present beneath the surface or an intergal part of it .................................... 13
13. Leaf scars present on twigs ......... Hypericum
13. Leaf scars essentially never forming on overwintering twigs; leaves dying and remaining attached, eventually partly disintegrating or part breaking off leaving an irregular surface .................. Phlox
12. Leaf blade with glands 0.05-0.1 mm across on 1 or both surfaces, sometimes in pits but sides of glands free of blade....................... 14
14. Twigs with abundant conspicuous whitish spreading hairs to 1.6(2.5) mm on all 4 sides ... Piloblephis
14. Twigs glabrous or with hairs to ca 0.2 mm, rarely also scanty hairs to ca 2 mm ........................ 15
15. Leaf blade underside with abundant minute straight erect hairs ............. Clinopodium
15. Leaf blade underside with scanty to abundant minute curved mostly ascending hairs.............. Conradina
3. Leaves alternate or mostly so .......................................................... 16
16. Stems prostrate .......................................................................... 17
17. Twig readily evident. Leaves well-spaced to somewhat congested; blade elliptic-oblong or elliptic-ovate to ovate or triangular ............. Vaccinium
17. Twig mostly hidden by leaves. Leaves much overlapping, narrowly elliptic to narrowly oblanceolate ......................... Pyxidanthera
16. Stems mostly decumbent to ascending or erect .......................... 18
18. Leaf blade 1-3 mm, sessile and clasping or sheathing twig; pith of year 2 twigs continuous ................................. Tamarix
18. Leaf blade 1-60 mm, sessile or with a short petiole; pith of year 2 twigs continuous or hollow .................................................. 19
19. Twigs or leaves or both hairy (sometimes sparsely so)...........20
20. Leaves with 3 major veins from base of blade .............................................................. Ceanothus
20. Leaves with 1 major vein from base of blade ....... 21
21. Year 2 twigs hollow, having no pith ................ 22
22. Plants erect or nearly so ........ Nierembergia
22. Plants spreading on or near ground .......... 23
23. Longest internode 0.5-1,5 mm Leaf blade needlelike to linear-subulate or scalelike ............................................... Hudsonia
23. Longest internode 2-13.1 mm. Leaf blade flat ................................................. Lechea
21. Year 2 twigs eith continuous pith ................... 24
24. Basal portion of petiole essentially parallel with twig ............................................................. 25
25. Leaf blade mostly 0.8-1.1 mm across, revolute to 270 ° .................................. Ceratiola
25. Leaf blade 0.7-8 mm across, revolute 90 ° or less ......................................................... 26
26. Leaf blade underside glabrous or with stalked glands; petiole 0.3-0.4 mm across ........................................ Leiophyllum
26. Leaf blade underside with ascending hairs; petiole to 1 mm across (See GROUP H) .................................................. Kalmia
24. Basal portion of petiole angled with twig ............................ 27
27. Leaf blade minutely and densely matted-hairy on underside (See GROUP H) Helianthemum
27. Leaf blade glabrous or hairs present and not matted .................................................... 28
28. Leaf blade mostly under 10 mm ........................................... Vaccinium
28. Leaf blade mostly over 10 mm ......... 29
29. Twigs densely hispid (See GROUP H)............................................... Kalmia
29. Twigs minutely hairy, never hispid (See GROUP H) ................................. Ilex
19. Plants glabrous (some with stalked glands)............... 30
30. Internodes prominently long on vigorous twig ...... 31
31. Leaf blade arising from upper edge of a sheathing stipule ............................................. Polygonella
31. Leaf or blade arising from stem at nodes ......... 32
32. Leaf blade 2-35 mm, fruits berries .............. 33
33. Leaf blade quite succulent ......... Lycium
33. Leaf blade somewhat coreaceous, not succulent ................................................. 34
34. Leaves 1 at tip of vigorous twigs ......................................... Vaccinium
34. Leaves 2-3 at tip of vigorous twigs (See GROUP H) ..................................... Ilex
32. Leaf blade 20-66 mm. fruits small achenes ...................... 35
35. Petiole not separating from stems, instead breaking apart, stubs remaining for several years ..................................... Chrysoma
35. Petioles falling from stems leaving scars .................................................... Baccharis
30. Internodes mostly or all quite short or uncommonly a few prominent ....................................... 36
36. Petiole or pttiolelike stalk lying essentially parallel with twig ............................................................ 37
37. Twigs glabrous, apex of leaf blade acute with a fine tapered tip, upperside of petiole glabrous ............................. Taxus
37. Twigs minutely hairy in narrow longitudinal bands, apex of leaf blade rounded to obtuse, sometimes with a short fine tip, upperside of petiole minutely hairy ............................................ Leiophyllum
36. Petiole otherwise or none ................................. 38
38. Main leaf blades spreading, narrowly columnar, fleshy, terete ....................................... Phemeranthus
38. Leaf blades spreading to appressed, flat, awl-shaped or linear (when terete or revolute, not fleshy)..................................... 39
39. Leaf blade nearly square in cross section .......................................... Ceratiola
39. Leaf blade flattened .................... Vaccinium