2 XCVIII. ACANTHACE^ (bURKILL AND CLARKE). 



in some strobilate spikes, the upper bracts may contain a solitary flower eacli» 

 while low^r "bracts" on the same spike may contain 2 or 3 flowers, and (though 

 beyond question homologous with tlie upper bracts) be termed, therefore, floral 

 leaves. 



The cliaracters taken from the pollen are exceedingly useful in determining whether 

 a single flower in a scrappy specimen is a liuellia or a DyscJioritte. But it must not 

 be supposed tliat the characters taken from pollen are more " absolute " than other charac- 

 ters. Thus, Lindau calls the ellipsoid pollen oi' Lepidanathis "honey-combed," but he 

 adds a caution that it is in many species only reticulated ; and, in some species, 1 

 should say that this reticulation is so broken and imperfect that it cannot be 

 differentiated from the granulated patches very generally present. In other words, 1 

 consider that there is a perfectly graduated series of pollen in the Acanthacece from 

 honeycombed through reticulated to smooth ; and above all in the Eujusticieoi, I con- 

 sider that there is a complete gradation from the " tubercled " pollen characteristic 

 of Jnsticia proper to that of Nicoteba (Lindau), Duvernoia, or Jihaphidospora. 



The difficulty, however, of subdividing Justicia, so that it may be possible to locate 

 a species definitely in one of its subgenera, is so enormous that any character 

 which assists to such a desired consumiimtion should be welcomed. When, however, 

 Lindau throws over inflorescence, bracts, anther-cells and anther-tails, capsule-dehis- 

 cence, number of seeds, nature of seed-coat, and forms a genus Nicoteba or Duvernoia 

 on pollen-characters only, we find the group contrary to nature itself; it appears to me 

 not a genus, but a handful of species taken at random from every part of the genus 

 Justicia (in a very wide sense). Nor am I able, by such pollen-characters, to refer a 

 plant to its genus. 



Throughout the Order, the most valuable characters for forming the larger groups 

 appear to be the number of ovules (either 2-1, or S-several, in each cell), the number of 

 stamens, the capsule and seeds. The combination of species in the Genera Plantarum 

 made by Bentham, on a mixture of these characters, appear to place like with like 

 much better than giving the pollen-characters a predominating value. 



Both Bentham and Lindau follow their predecessors in giving a high value to the 

 elastic risina: of the placenta in the fruit of Rungia, &c. I have here followed them ; 

 but the giving this character a prepotent influence appears to me to separate like from 

 like nearly as flagrantly as the pollen-character when similarly applied as of pre- 

 dominant value (see the observations in table of genera upon JRungia, Macrorungia, 

 Dicliptera). 



The large strong retinacula holding up the seeds usually suffice to refer a plant to 

 this Order. The first 3 genera, where this character fails, are so strongly marked in 

 other ways that they are easily recognised. A special eye should be kept on Nelsonia 

 and Synnema, as these plants have been sometimes, on a hasty inspection, sorted into 

 ^crophulariace(e. 



Excluded genera. 



CoiNOCHLAMYS, T. Anders., is Loganiaceous. 

 Cyclociieilon, Oliver, is Verbenaceo'.is. 



Tkide I. Tliunbergieaea — Corolla-lobes contorted in the bud {no lobe wholly 

 within or wholly without the others). Two collateral ovules in each cell. Seeds globose 

 or orbicidar, ivithout retinacula. 



Fruit fleshv with one cell only 1. Afromendoncia. 



Fruit dry with a distinct beak, 2-celled . . . .2. Thunbergia. 



Tribe II. XTelsonieae. — Calyx in the African species A-partite. Corolla-lobes 

 imbricate, the posterior lobes outermost. Stamens 2. Ovules in .each cell many, 

 superjwsed in tico series. Seeds small, globose, without retinacula. 

 Spikes dense, slender, covered with bracts below the flowering 



portion . .3. Elytrarta. 



Spikes dense, more or less ovate, sessile or with a naked 



peduncle 4. Nelsonia, 



