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Bartonia

Leaf arrangement is an important character in Bartonia, but it has been given too much weight. It is important to realize that it does display variation, and rare individuals within a population will show different character states (e.g., B. virginica with alternate leaves). Other characters, such as corolla and anther morphology, need to be considered as well. When measuring the length of the stigmas, be sure to measure the basal portion that is decurrent onto the ovary. Timing is also important as the stigma does not reach its full length until mid- to late August. At this time, the ovary is rather plump and most of the anthers will have fallen from the stamens. Reference: Gillet (1959).

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B. virginica
1a. Stigmas, including the basal lobes, (1.3–) 1.5–2.3 mm long at maturity; petals oblong, rounded to obtuse at the apex and with a short, but prominent, apiculus; anthers apiculate at the apex; capsules dehiscing from the apex to a point proximal to the stigmas; stems with opposite leaves [Fig. 664], the nodes becoming progressively more crowded near the base
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1b. Stigmas 0.8–1.5 mm long at maturity; petals lanceolate to oblong-lanceolate, acute at the apex and usually without a clear apiculus; anthers rounded at the apex or rarely with an apiculus in B. iodandra; capsules dehiscing from the apex to the base of the stigmas; stems with alternate leaves, the nodes not or scarcely becoming more crowded near the base
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  B. paniculata
  2a. Petals lanceolate and acute at the apex; filaments green to yellow-brown, except sometimes near attachement of anther where purple; anthers usually yellow, 0.3–0.5 (–0.6) mm long; branches of inflorescence ascending to spreading; stems often slender and lax, usually green; calyx essentially distinct
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  B. iodandra
  2b. Petals oblong-lanceolate, acute at the apex or infrequently with an obscure apiculus; filaments purple (rarely green to yellow-brown); anthers usually purple, (0.4–) 0.5–0.6 (–1) mm long; branches of inflorescence erect to strictly ascending [Fig. 664]; stems stouter, strict, usually purple or tinged with purple; calyx often shortly connate near the base

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