3 
have found to match with some specimens of Boivin’s. Their leaves 
are considerably larger than those of Petit Thouars’ plant and their 
venation is said to be ‘ bien visible en dessous.’ The inflorescence and 
the flowers, including the corolla, are described as slightly pubescent, 
and the corolla lobes as somewhat shorter than the tube and rather 
broad. In view of the differences indicated, some element of uncer- 
tainty as to the identity of their plant with that of Petit Thouars still 
remains. ‘The plant collected by Guillot, on the other hand, has been 
compared and identified by M. Hochreutiner with the plant of Thouars, 
which is the basis of the description drawn up by Hochreutiner. 
Baillon in Histoire des Plantes, l.c., says of Plectaneia, of which 
he knew but one species, viz. P. Thouarsit, ‘ fauce squamulis 5 cum 
staminibus alternantibus subobturata.’ Such scales or tubercules 
are shown in fig. 3 of this plate. But sections made through the 
corollas of P. Thouarsii as well as P. elastica show that the walls of 
by Baillon for throat scales such as exist in various other Apocynaceae. 
Neither Jumelle and Perrier, nor Hochreutiner mention such bodies 
in their descriptions of species of Plectaneia. 
According to Professor Jumelle and M. Perrier de la Bathie, 
P. elastica yields a rubber of good quality. They state that 1 litre of 
the latex of ‘ piraovaovao ’ yields 16-18 grammes of dry rubber. The 
Sakalaves cut the stems down in order to obtain the rubber, but the 
French authorities suggest that old stems which reach 20 cm. In 
The coagulation of the 
latex is brought about by the natives by exposure to the sun and subse- 
P. exastica : flowering branch and fig. 1, flower ; 2, pistil and part of calyx; 
3, corolla, opened out; 4, anthers; 5, transverse section of ovary; 6, longi- 
A 
tudinal section of ovary. enlarged. 
. ARSII: fig. 7, section through the follicles before they have begun to 
separate; 8, a fruiting branch; 9, a seed, All enlarged except 8, which is of 
natural size. ‘ 
