36 



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



de Saint Pierre (1. c.) and others. In this respect the genus 

 Posidonia differs from most of the other sea-grasses, since floating 

 of the reproductive organs is a very rare phenomenon amongst 

 them (cf. Cymodocea antarctica). 



The Mediterranean species (P. oceanica) is very like our Au- 

 stralian one, still it differs in several points as regards the in- 

 florescence, the flower and the shape of the fruit, as well as in 

 the structure of the leaves. P. oceanica is said to flower and set 

 fruits only very rarely, while it appears that the Australian spe- 

 cies flowers more regularly, and the enormous masses of fruits 

 which I found both at Carnarvon and especially at Geraldton, 

 show that the species set fruits in abundance, at least periodi- 

 cally. 



At what time it flowers is not known with certainty, but to 



Fig. 22. Posidonia australis, from Géraldton. a, The irregularly three-lobed 



exocarp opened, b and c, Two different fruits, showing the splitting of the 



exocarp beginning at the base, d and e, "Stones" of b and c; the plumule 



protruding at the apex, f, Embryo (of e). (About 5 / 4 nat. size). 



judge from analogy with P. oceanica, which flowers in the autumn 

 and ripens its fruits in the next spring, the flowering of P. au- 

 stralis should take place during the autumn of the southern he- 

 misphere, i. e. in March — May, and the fruits should ripen in 

 the spring, i.e. September — November; the latter supposition is 

 confirmed by the fact that I collected the ripe fruits during the 

 last days of October. 



I hope that some Australian botanist will be able to study 

 on the spot the flowering of this species and the development 

 of the fruit, which has several interesting points still unsolved 

 (e. g. the fate of the coats of the ovule). 



Posidonia sp. 



I found at Carnarvon, besides the typical broad-leaved P. 

 australis, some narrower leaves like those of a broad -leaved Zostera. 



