34 



Dansk Botanisk Arkiv, Bd. 2. Nr. 6. 



Fig 19. 



Posidonia australis. Diagram 

 of an inflorescence. 



sclerenchyma-strands at the points where the septa between the 



lacunæ (air-chambers) meet. (The structure of some doubtful 



Posidonia-ledives is dealt with 

 later, p. 37). 



The inflorescence is terminal 

 on a long naked axis. It is 

 distichous and branching, and 

 consists of about three branch- 

 spikes and the terminal spike; 

 these are supported by and en- 

 veloped in bracts with large 

 sheaths, the leaf-blade being 

 short or absent. A diagram 

 (Fig. 19) of an inflorescence 

 shows the arrangement of the 



bracts and spikes. The lowermost bract has a blade longer than 



the sheath, while the blades become gradually reduced in size 



in passing up the inflorescence. The two lowermost lateral spikes 



are more or less long-stalked, and their bracts are placed towards 



the upper end of the axis, while the uppermost lateral spike has 



its bracts nearly in the axil of the supporting 



bract of the main axis. All the lateral spikes 



begin with a short bladeless prophyllum in 



the axil between the main axis and the branch. 



The number of bracts immediately supporting 



the spikes varies from two to four. Each 



spike bears 4 — 6 (perhaps sometimes more) 



flowers placed at some distance from each 



other; the axis is continued into a horn-like 



process above the uppermost flower (which 



consequently is lateral like the other ones). 

 In Posidonia oceanica it is stated that the 



uppermost flower of each spike is male while 



the others are hermaphrodite. I have not had 



flowering material of P. australis at my dis- 

 posal, but to judge from the fruiting specimens Fig 20 Posidon i a au . 



all the flowers seem to be hermaphrodite in $tralis,i romGera]dton. 

 . . _,. _ m . • +i A lateral fruiting spik- 



this species (see Fig. 20). There is no perianth. elet ( Nat size f 



The broad connectives of the three sessile 

 anthers are persistent on the fruit. Their shape is somewhat var- 

 iable, being shorter or longer ovate-lanceolate with a broad base 

 and a more or less obtuse apex (not nearly so acute and pointed 



