10 GEAF ZU SOLMS-LAUBACH— MOXOGExVPH OF THE ACETABULAEIE.E. 



support it in the fossil material, has been more recently proved true in the most brilliant 

 fashion by the discovery of a living species of this genus. Of this species I found first 

 specimens from Martinique in the Berlin Herbarium, then several from Guadeloupe in 

 Herb. Thuret, but later I found that it had been described as A. SchencMi, Mobius, from 

 specimens gathered by Dr. Schenck, at Cabo Prio in Brazil. I was unable, however, to 

 satisfy myself of this determination until I had received the original specimens from the 

 discoverer. Nothing was to be made of the description of the plant, which did not 

 mention the principal peculiarity. The cap-bearing shoots of AciciUaria Schenckii 

 (Plate III. fig. 14) agree in all essential points of external structure with those of 

 Acetabularia, section Acetabuloides. Their sporangial rays are rather closely united ; 

 the coronse superior and inferior are well developed and agree in form with those of 

 A. caraibica. While the sporangial rays of Acetabuloides contain numerous round free 

 spores, in this plant each ray contains a small body that exactly corresponds in form and 

 structure with the lime-spiculse described for Acicularia. It consists of a strongly calcified 

 substance enclosing numerous cavities lying near the surface, and consequently trans- 

 parent. In each of these and completely filling it there is a spore of the same structure 

 as those of Acetabularia (Plate III. figs. 9, 15). It follows that the pits of the fossil forms 

 are spore-containing cavities from which the spores have disappeared and the external lime- 

 covering has not been preserved, so that they appear as opening outwards. If such a spori- 

 ferous spicula be treated with dilute acid, there remains as the substratum of calcification 

 a slime of small consistency, which surrounds the sppre-cavities and is quite homogeneous, 

 showing no diflPerentiation either superficially or internally, except that here and there 

 among the spore-cavities and occupying exactly the middle there are triangular or quadran- 

 gular spaces. The spores themselves are globular, with a sharply outlined, rather thin 

 membrane, provided with a lid in the usual way. In consequence of drying they have often 

 collapsed in the form of a basin or dish, exposing a part of the spore-cavity, from which it 

 may be inferred that in the mature condition they lie free within it. On treatment with 

 sulphuric acid the membrane swells up exceedingly, and on its surface there appears a 

 very delicate, tightly-stretched membrane, with a sharp contour, which finally bursts and 

 sinks down folded up, proving to be a very delicate cuticle-like lamella {of. Plate III. fig. 9). 

 If we turn to the careful examination of the unaltered spicula in order to obtain a 

 clear understanding of the origin of the slimy substratum of the calcification, we see that 

 the lime-mass does not possess equal thickness at all places, but that each spore is sur- 

 rounded as with a shell by a wall-like ring of maximum calcification. These shells 

 appear to be stuck to each other by a shght lime-incrustation in the interstices, and the 

 above-mentioned angular spaces, quite without lime, are to be found here and there in an 

 unaltered state. A view of the whole gives the impression that the slimy substance has 

 originated by a transformation of the outer layers of the spore-membrane, and that these 

 are afterwards united into a firm mass by calcification. If the slime were the remainder 

 of the protoplasm of the sporangial ray not used in the formation of the spores, as might 

 very well be the case, then it would be impossible to understand why it is not evenly distri- 

 buted, and why its density should decrease in so striking a way in the direction of radii from 

 each spore. However, there is opposed to this view the circumstance that the membrane 



