Hedera

Ackerfield, Jennifer & Wen, Jun, 2002, A morphometric analysis of Hedera L. (the ivy genus, Araliaceae) and its taxonomic implications, Adansonia (3) 24 (2), pp. 197-212 : 210-211

Key to Taxa of Hedera

1. Trichomes stellate, large (0.5-1 mm), with fewer than 10 rays, white in color .......................................... 2

1’. Trichomes scale-like, small (0.1-0.4 mm), generally with more than 10 rays, reddish brown or white in color .................................................................................................................................................................. 6

2. Trichomes parallel to leaf surface .............................................................................................................. 3

2’. Trichomes at a right angle to leaf surface .................................................................................................. 4

3. Length from leaf base to first sinus 2.5-4 cm, juvenile leaves located 6-8 nodes below the apex large (6-9 cm across), 5-lobed, petioles long (5-12 cm), rhizomes absent ...................................................... H. hibernica

3’. Length from leaf base to first sinus 1.5-2 cm, juvenile leaves located 6-8 nodes below the apex smaller (3.5- 6.5 cm across), 3-5-lobed, petioles short (3.5-5.5 cm), rhizomes present ...... H. helix subsp. rhizomatifera

4. Mature fruits orange/yellow, found only in Italy and western Transcaucasia .............. H. helix f. poetarum

4’. Mature fruits black, found throughout Europe or the Azores .................................................................... 5

5. Juvenile leaves located 6-8 nodes below the apex large (5-8 cm across), 3-5/-7-lobed, with few to no white markings on the veins, length from leaf base to first sinus 2-4 cm .............................................. H. azorica

5’. Juvenile leaves located 6-8 nodes below the apex smaller (3-6 cm across) and usually 5-lobed, with white markings on the veins, length from leaf base to first sinus 1-2 cm .............................. H. helix subsp. helix

6. Juvenile leaves always unlobed and very coriaceous, fresh leaves strong-scented when crushed .. H. colchica

6’. Juvenile leaves lobed, fresh leaves not strong-scented when crushed .......................................................... 7

7. Juvenile leaves located 6-8 nodes below the apex large (5-8 cm across), lateral lobes generally longer than or as long as the middle lobe ........................................................................................................................ 8

7’. Juvenile leaves located 6-8 nodes below the apex small (2-4.5 cm, rarely 6 cm across), lateral lobes only about half as long as the middle lobe (except for H. rhombea ) ................................................................ 11

8. Base of juvenile leaves truncate or only slightly cordate, leaves glossy on adaxial surface ........ H. algeriensis

8’. Base of juvenile leaves cordate or slightly truncate, leaves matte or glossy on adaxial surface ...................... 9

9. Center of trichomes not raised, juvenile leaves located 6-8 nodes below the apex 5 -lobed .... H. maroccana

9’. Center of trichomes raised, juvenile leaves with 3-5-lobed ...................................................................... 10

10. Junvenile leaves generally 5-lobed ........................................................................................ H. maderensis

10’. Juvenile leaves unlobed or 3-lobed ...................................................................................... H. canariensis

11. Mature fruits orange/yellow, found in Nepal or southwestern China...................................................... 12

11’. Mature fruits black, found elsewhere ...................................................................................................... 13

12. Juvenile leaves generally with much lateral lobing, usually 5-lobed (rarely 3- lobed) .................................... ...................................................................................................................... H. nepalensis var. nepalensis

12’. Juvenile leaves generally with little or no lateral lobing, usually 3-lobed ............ H. nepalensis var. sinensis

13. Juvenile leaves with distinct white markings on the veins ........................................................................ 14

13’. Juvenile leaves without distinct white markings on the veins, or only very slight white markings present .... 15

14. Trichomes present only on abaxial juvenile leaf surface ................................................................ H. cypria

14’. Trichomes present on both abaxial and adaxial juvenile leaf surface .................................... H. pastuchovii

15. Leaf base truncate or only slightly cordate, leaves 3-lobed .......................................................... H. iberica

15’. Leaf base cordate, leaves 3-5-lobed .......................................................................................... H. rhombea