New Ceropegia from Laos 
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small and, most importantly, the basal inflation of the corolla tube (ostiolum) is basally 
constricted. This latter character is significant and of high taxonomic value in, for 
example, African Ceropegia. Therefore, Maxwell's (2009) determination as C. thorelii 
cannot be confirmed here. Instead, although the corolla of Ceropegia cochleata Kidyoo, 
with its long-tailed, twisted lobes, does not show much similarity with the relatively 
short and obtuse corolla lobes of the new species, Ceropegia cochleata and C. laotica 
are vegetatively, ecologically and geographically much closer. They share the trailing 
to twining (when support is available) habit and growth form; they have wiry stems 
and spreading, fairly small, more or less lanceolate leaves; they have similar habitat 
preferences as they both occur on sandstone rocks with sparse soil and vegetation 
cover dominated by grasses and mosses (Kidyoo, 2015b); both species develop small 
tubers; and the above-ground parts do not survive the dry season. 
There are also a number of similarities in habit, ecology and flower morphology 
between Ceropegia laotica and C. digitiformis Kidyoo. The latter species is found in 
Thailand in the Phu Wua Wildlife Sanctuary and Phu Langka National Park, c. 400 km 
northwest of the type locality of C. laotica. However, although Ceropegia digitiformis is 
also deciduous, the aerial stems survive the dry season because they are fleshy (Kidyoo 
& Paliyavuth, 2017), and not wiry as in C. laotica. Also the leaves are laminar, elliptic, 
ovate to rounded in Ceropegia digitiformis (and not rather linear and fleshy as in C. 
laotica ) - displaying a close relationship to the Indian C. thwaitesii Hook. Kidyoo & 
Paliyavuth (2017) distinguish Ceropegia digitiformis from C. thwaitesii only on small 
deviations in corona morphology. In addition, Ceropegia digitiformis is unlikely to be 
a sister species of C. laotica because of the pollinarium morphology. The shape of the 
pollinium in Ceropegia digitiformis is ovoid with the germination crest subapical (cf. 
Kidyoo & Paliyavuth, 2107: figs. IF and 2E), whereas the pollinia in C. laotica (and 
C. cochleata ) are broadly ovate to (sub)rectangular with the pellucid margin along the 
inner side of the pollinium (Fig. 2f). On the other hand, Ceropegia digitiformis and C. 
laotica share the character of a stipitate corona although the interstaminal lobules in 
C. laotica are not linear-lanceolate as in C. digitiformis, but rather triangular and much 
more similar to those of C. cochleata, including in indumentum. 
To conclude, Ceropegia laotica, C. cochleata and C. digitiformis all inhabit 
rocky, montane habitats on sandstone with sparse vegetation in the central Indochinese 
Peninsula. They share a number of morphological similarities but can each be 
distinguished by unique morphological characters. In the important habit, leaf and 
corona/gynostegial characters, we regard Ceropegia cochleata as presumably most 
closely related to our new species. 
ACKNOWLEDGEMENTS. This study is part of an on-going research project on the 
systematics of Asian Apocynaceae. Financial support was received from the National Parks 
Board (Singapore) which sponsored numerous field trips to Laos and herbarium study trips 
to Asian and European institutions. The curators of the E, P and SING herbaria are thanked 
for allowing access and/or for allowing loans or high quality images of herbarium specimens. 
We thank two anonymous reviewers and Dr David Middleton, Editor of Gardens’ Bulletin 
Singapore, for suggesting improvements to this manuscript. 
