324 ALDROVANDA VESICULOSA. Chap. XIV. 



prominence. These processes are formed of very 

 delicate membrane lined with a layer of protoplasm ; 

 and they sometimes contain aggregated globules of 

 hyaline matter. Two of the slightly diverging arms 

 are directed towards the circumference, and two 

 towards the midrib, forming together a sort of Greek 

 cross. Occasionally two of the arms are replaced by 

 one, and then the projection is trifid. We shall see in 

 a future chapter that these projections curiously re- 

 semble those found within the bladders of Utricularia, 

 more especially of Utricularia montana, although this 

 genus is not related to Aldrovanda. 



A narrow rim of the broad flat exterior part of each 

 lobe is turned inwards, so that, when the lobes are 

 closed, the exterior surfaces of the in-folded portions 

 come into contact. The edge itself bears a row of 

 conical, flattened, transparent points with broad bases, 

 like the prickles on the stem of a bramble or Eubus. 

 As the rim is infolded, these points are directed 

 towards the midrib, and they appear at first as if they 

 were adapted to prevent the escape of prey ; but this 

 can hardly be their chief function, for they are com- 

 posed of very delicate and highly flexible membrane, 

 which can be easily bent or quite doubled back with- 

 out being cracked. Nevertheless, the infolded rims, 

 together with the points, must somewhat interfere 

 with the retrograde movement of any small creature, 

 as soon as the lobes begin to close. The circum- 

 ferential part of the leaf of Aldrovanda thus differs 

 greatly from that of Dionaea ; nor can the points on 

 the rim be considered as homologous with the spikes 

 round the leaves of Dion?ea, as these latter are pro- 

 longations of the blade, and not mere epidermic 

 productions. They appear also to serve for a widely 

 different purpose. 



