8 GEAF ZU SOLMS-LAUBACH— MONOGRAPH OF THE ACETABUL ARIE.E, 



by a slimy, soft substance, which opposes little resistance to a dissecting needle, and i* 

 often so soft that its consistency is destroyed by the evolution of gas in the action of tht^ 

 acid. In how far this substance represents the swollen middle lamella of a circular 

 cushion of united chambers originally closed like Acetabularia mediterranean or wholly or 

 in part the cohesive product of the disorganization of the outside of the originally free 

 walls of the ray as in FoJijphysa, cannot be certainly determined without a knowledge 

 of development unobtainable from dry material. Be this as it may, in any case 

 A. Caly cuius and A. FarloioH, in all other respects true Acetahularicr, agree in this 

 point in the mature condition with JPolyphysa. There is otherwise such a series of 

 intermediate cases that this character does not maintain any systematic significanc(\ 

 Eor this reason I have thought it right to sink the genus Polyphysa^ distinguished only 

 by the absence of a well-developed corona inferior, and to regard it as only a section of 

 Acetabularia. 



Acetabuloides appears to include numerous species falling under several groups 

 within which they are to be distinguished only with difficulty. A definite elucidation of 

 all these forms is not possible on the basis of the generally meagre specimens preserved 

 in herbaria. Various doubtful specimens have consequently not found a place in this 

 paper. The classification given here is less concerned with the natural relationship 

 than with an attempt to attain a ready key to the naming of species. Otherwise 

 A. Farlowii, n. sp., and A. Suhrii^ n. sp., would probably have been brought nearer to 

 the group of A. crenulata and A. caraibica ; while A. dentata, n. sp., would be separated 

 from it. A. Calyculus^ Quoy et Gaim., would be isolated, and the three species dis- 

 tinguished by the size of their caps, A. Kihieri, J. Ag., A. major, Mart., and A. Gigas, 

 n. sp., would form a natural group. In these three species the radial walls dividing the 

 chambers of the cap show a common peculiarity first noticed by J. Agardh in his 

 A. Kilneri (Plate I. fig. 6), The section of the radial wall shows a broad, soft, slimy 

 middle layer, and two coarse layers bordering the lumina of the chambers. These show 

 perpendicular stratifications irregularly distributed, but often in groups, passing out 

 towards the slimy middle layer and not towards the lumen, and sometimes alternating 

 with each other like notches. If one tears the chambers apart to view these stratifi- 

 cations from the surface, it appears that they are not equally developed over the whole 

 surface of the wall, but most strongly at the upper and lower margin, decreasing, 

 flattening out, and vanishing imperceptibly towards the middle. Plate I. fig. 6 a shows 

 them in normal position from one side of the surface of the cap ; Plate I. fig. 6 6 in 

 oblique surface view obtained by pressing asunder the two lamella?. 



Enough has been said to lay a foundation for the appreciation of the genus Acetabn- 

 laHa as understood here. A peculiarity is to be mentioned, however, which occurs only 

 very rarely in other species, but appears to be characteristic of A. crenulata in its 

 normal development, viz. : the shoot, after forming the first cap, grows through it and 

 produces several others in succession. Specimens of this species are common enough with 

 several caps of unequal development abovi^ each other (Plate I. fig. 1) ; very often only the 

 uppermost remains, and thick nodular swellings, with scars, shoAv the places on the stalk 

 where former caps have fallen off. Between every two of such caps there is a whorl of 



