130 The Irish Naturalist. June, 



10. Does the species ever ripen viable seeds ? — I believe it will 

 be found that most plants which are genuine natives of any 

 countr}' produce fully ripened seeds at some period of their 

 history. Various causes may operate to prevent this, such as 

 coldness of climate, or absence of fertilisation due to the 

 flowers being unisexual and all of the same sex, as in Cana- 

 dian Water-Thyme. In other cases where the flowers are 

 hermaphrodite self-fertilisation is apparentl}' ineff"ective, as in 

 Lysimachia Nu7n?milaria. Linn., and Acorns Calamus, Linn. 



Care must be taken, however, in applying this test. Mr. 

 Clement Reid states that after watching Rtiscus aculeatus^ Linn., 

 in England for twelve years he found that, as a rule, only one 

 plant in fifty produced any fruit. Ostenfeld mentions 36 

 species which scarcely ever ripen their fruits in the Faeroes. 

 F'ive of these never even flower. 



1 1. What are the iiatural methods of distribution of the species 

 U7ider cojisideration ? — On this subject we have still a great 

 deal to learn with regard to the plants found in Ireland. 

 There are four outstanding methods of dispersal, namely, by 

 {a) spontaneous ejection, {b) water, (c) wind, {d) animals. 



{a) This method only serves to distribute the species over 

 short distances. The other three methods might conceivably 

 be the means of occasionally introducing new species into our 

 island, and of rapidly disseminating them over the country. 



{b) Extensive investigations were carried out by Guppy to 

 determine the transporting power of fresh water, sea water, 

 and ice. One fact will suffice to show the value of his obser- 

 vations. He found that fruits of Spargaiiiuni 7'aniosum^ Huds., 

 germinated after being twelve months afloat in sea water. 

 As another striking instance of the transporting power of 

 water, we know that West Indian seeds are cast up on the 

 west coast of Ireland. Maury, in his Physical Geography 0/ 

 the Sea, mentions the case of a bottle thrown over off Cape 

 Horn being picked up subsequently on the coast of Ireland. 



{c) The transporting power of wind over fruits and seeds 

 provided with wing-like expansions or parachutes formed of 

 hairs, is well knovv^n. Definite experiments showing the exact 

 distance over which the wind can carry such seeds and fruits 

 would be a welcome addition to our knowledge. Ernst states 



