Neomeris dumetosa , L amour. 
595 
the fall of the filamentous portion, the whorl of gametangia 
would then persist on the main axis much as in the older 
stages of Stage II. This second type of leaf occurs again in 
the adult plant of Cympolia barbata , where according to 
Cramer 1 , the non-calcified whorls of the nodal portions of the 
axis are of this type, and, when first formed, bear the full 
filamentous terminal portion. 
Again, the remarkably symmetrical habit of one of these 
whorls of short members suggests nothing so strongly, at first 
sight, as the cap of Acetabularia. The publication of Solms- 
Laubach’s important monograph of the Acetabularieae 2 , just 
as the present paper is being completed, enables me to 
compare the hypothesis now put forward with the results 
obtained for these highly aberrant types of Dasycladaceae. 
Solms-Laubach concludes, from a careful comparison of 
species of Polyphysa and Acetabularia , that the ray-segments 
of Acetabularia mediterranea are to be regarded as, not so 
much a whorl of lateral appendages, as a development of 
lateral sporangia on the sides of appendages which have 
become extremely reduced and distorted, and he presents 
a series of types in support of his opinion ; but the older view 
of the morphological value of the cap of A. mediterranea 
seems so simple in comparison with the new one, that until the 
former has been definitely proved to be impossible, it will 
doubtless retain adherents. Again, Solms points out the 
difference between the Acetabidum section comprising A. 
mediterranea alone, and the Acetabuloides section, and here 
perhaps the possibility is not excluded, that, granting that the 
cap-type of thallus represents a form which has proved itself 
a success in relation to special environment, a cap may have 
been evolved at different points in the phylogeny of the 
group, and that these may resemble each other by con- 
vergence of type. Thus, according to the older view, the 
formation of a cap- whorl in A. mediterranea seems to be 
accompanied by a telescoping of the main axis in the neigh- 
1 I. loc. cit., Taf. IV, Fig. 4. 
2 Trans. Linn. Soc., Vol. v, I. 
