Remarks on the structure of the Fruit of Rhipsalis. 469 



On the Structure of the Fruit of Rhipsalis. 

 The fruit of Rhipsalis has been considered to possess a different 

 structure from that of all other Cacteae, in having placentae in the 

 axis of the berry instead of on the paries, and the berry itself has 

 also been considered as probably trilocular, whilst those of all other 

 genera in the order are unilocular. Hence De Candolle has placed 

 it in a separate tribe, his Rhipsalideae, expressing, however, some 

 doubts about the accuracy of the observations upon which he has 

 founded his arrangement. In his last memoir on the Cacteee (1834,) 

 he separates Rhipsalis salicomioides from the rest, under the generic 

 name of Hariota ; and in that species he states that he had ascer- 

 tained the ovary to be unilocular, and the placentae parietal. I have 

 lately had an opportunity of examining the fruit of Rhipsalis cas- 

 sytha in all stages of its growth, and can safely assert that both 

 suppositions, of its being trilocular and having central placentae, 

 have originated in a mistake. When the fruit is ripe, the seeds 

 are nestled in the midst of a very liquid pulp, and are no longer 

 attached to any part ; but in earlier stages of its growth, they are 

 found to adhere in double rows upon three placentae, disposed lon- 

 gitudinally on the paries. At first sight there is a deceptive ap- 

 pearance of three dissepiments, or at least of three inwardly pro- 

 jecting placentae, to the innermost extremities of which the seeds 

 are attached ; but further examination shews this to arise, mere- 

 ly from the close agglomeration of the funicular 

 chords (see Fig. A,) which stretch from the paries 

 towards the axis, and from whose extremities the 

 ovules are suspended in a reversed position. The 

 placentae themselves scarcely form any projection 

 on the paries, as is very evident in some cases 

 where many of the ovules have become abortive ; A 



and, indeed, several are so in all cases, and then appear as small 

 brown spots attached to the paries. It seems to me likely that the 

 watery pulp in which the seeds are nestled in this and other genera 

 of the order is derived from the super- developement of the cellular 

 tissue of the funicular chords. The whole coat of the berry, form- 

 ed by the union of the calyx tube and pericarp, is very succulent, 

 but the interior pulp is much more so ; and this does not appear 

 any way connected with, or to originate from the inner coats of the 

 pericarp, but in the way here suggested. Be this as it may, it is 

 sufficiently evident that the ovary and fruit of Rhipsalis are strictly 

 unilocular with parietal placentae, as in all other Cacteae, and, con- 

 sequently, it is necessary that the tribe Rhipsalideae should be sup- 

 pressed. 

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