Order 89. Acanthacece. 227 



ORDER 89. ACANTHACEJE, 



Herbs or shrubs, with opposite undivided leaves without 

 stipules ; flowers with tubular corolla, generally 2-lipped, 

 sometimes of 5 nearly equal lobes, the calyx usually small and 

 surrounded by bracts, which are often very conspicuous, and 

 also by bracteoles ; stamens on the corolla, 4, didynamous, or 2, 

 anthers generally 2-celled, often conspicuously so ; ovary 

 superior ; fruit a capsule, the seeds generally attached to hooks 

 (retinacula) which form part of the placenta. 



This is a very large order, almost confined to the tropics, and there 

 are far more species in W. India belonging to it than to any of the 

 other didynamous orders, and an unusually large proportion are 

 decidedly common. On the other hand, scarcely any species are 

 cultivated either for their flowers or for useful products. The bracts 

 are in very many cases sufficiently conspicuous to mark the order 

 from others having similar flowers, and many species are glandular 

 and strong, smelling. So Milton speaks correctly of 



" Acanthus, and each odorous bushy shrub." 



The undivided ovary distinguishes the order from Labiatae, the 

 fruit and seeds generally from Scrophularinese, the same parts and 

 the habit from Bignoniacese. 



Note 1. I have not found any help from H's division into 

 5 tribes, and in order to keep the diandrous and didynamous 

 genera separate have slightly varied H.'s order. 



Note 2. I have not generally thought ifc necessary to 

 describe bracteoles as well as bracts. The bracteoles usually 

 resemble the calyx segments. 



Note 3. In many species the anther cells are so separated 

 as to give the appearance of double, or, as the old writers called 

 them, twin anthers. 



Note 4. As regards the genera described below : 



In gen. 1 and 16 there are no retinacula. 



In gen. 2, and in some species of 11, the leaves are much 

 divided. 



In all the genera from 8 onwards, except 18 and 19, the 

 capsule is 2 or 4-seeded, generally the latter. 



In gen. 10, 11, and 13, the corolla has only one lip. 



A large proportion of the plants have flowers either white or some 

 shade of blue and purple. At the foot of the Himalayas, and at a 

 small elevation, Hooker found " the white or lilac blooms of th 

 Convolvulus-like Thunbergia and other Aoanthaceae to be the p-e- 



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