64 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



of the wind, no agency is more in requisition for the 

 dissemination of plant-germs. But notwithstanding 

 this, hygroscopic agency seems to play only a sub- 

 ordinate role in the distribution of plants. We have 

 but to consider how limited is the range of this 

 force, to see that it must be so, and that the hygro- 

 scopic property is chiefly of value in relation to other 

 and more efficacious agencies. 



4. Water Transport. — A seed, the weight of 

 which in air would at once cause it to fall to 

 the earth, may, on account of the greater density 

 of water, remain suspended in that liquid sufficiently 

 long for the gentlest current to carry it a consider- 

 able distance. Hence it comes that special provisions 

 for transport by water are seldom required, and 

 have been observed only in a very limited number 

 of plants. 



The non-ciliated antherozoids of the Floridese, or 

 red seaweeds, as we have seen, are transported by 

 this means. According to Dodel-Port, the fertilising 

 currents in this case are often due to an animal. 

 It seems that on the fronds of these algae the 

 ciliated infusorian Vorticella grows abundantly. 

 This elegant little organism, with its exquisitely 

 formed bell and delicate spii-al stem, might be" 

 described as a miniature lily, but for the trans- 

 parency of its tissues and the activity and energy 

 of its movements. The animal at will can lengthen 

 or shorten its stalk ; and by alternately extending and 

 retracting it, Vorticella imparts to its bell a graceful 

 rhythmic motion. This movement, aided by the 

 action of the cilia with which the bell is fringed, 

 gives rise to tiny whirlpools in the surrounding 

 water. By the vortices so caused, currents are 

 generated which assist in the fertilisation and 

 dissemination of the Floridese. For the reception 

 of the antherozoids there is here also associated 

 with the archegonium a special filament — the tricho- 

 gyne — to which these corpuscular antherozoids 

 adhere. Except in those cases where the spore 



