264 The Scottish Naturalist. 



Special adaptations occur in the water-lilies so commonly to 

 be found in Scottish lochs. The fruit in both the white and the 

 yellow water-lilies contains several spaces ranged round a cen- 

 tral column like the spaces between the spokes of a wheel : in 

 these lie numerous seeds. In the yellow water-lilies (Nuphar) 

 the outer coat of the fruits alone splits open when the seeds are 

 ripe, and the inner layer enclosing each of the various divisions 

 splits away, containing the seeds and also enough air to buoy 

 up the whole on the surface, where it floats for a time, driven 

 about by winds or currents till a hole forms in the wall and 

 seeds drop out and sink to the bottom of the loch. There they 

 germinate in the mud. In the white water-lily (Nymphcea) the 

 seeds are set free when the fruit splits ; but each seed has a 

 coat that has grown up from the funiculus or stalk loosely 

 round it so as to cover it, enclosing air enough to float the seed, 

 and thus to allow of its conveyance to some distance. On the 

 decay of this coat, and the escape of the air, the seed sinks to 

 the bottom. 



Adaptations for conveyance attached to the bodies of animals. — 

 Sticky secretions very seldom form the means among our 

 native plants ; never, in fact, as regards the seeds themselves, 

 one might say, though the seeds of Linuni and of a few other 

 plants become sticky when moistened. The fruits of a few 

 show a similar quality, and the ovary of Linnoza borealis is said 

 to be sticky when ripe by reason of gland hairs. In some 

 Labiates, the calyx, which breaks away with the fruits, is sticky 

 for the same reason. 



Prickles or hooks form by far the most frequent means for 

 attaching the fruits to the bodies or limbs of animals. It may 

 be said that no Scottish plants show structures of this kind on 

 the seeds themselves — indeed seeds so provided are rarely met 

 with anywhere. The surface of the ovary sometimes bears 

 many small prickles (e.g., Ranunculus arvensis, Cynoglossum offici- 

 nale) ; or, as in some exotic genera, it may bear one or more 

 spines or hooks of considerable size. A well-known example is 

 the fruit of the " Wait-a-bit Thorn " of South Africa (Harpa- 

 gophytum), with hooked branched spines an inch long, and very 

 strong. These fruits are said to be very injurious to sheep 

 through sticking in their wool, and irritating the skin when the 

 sheep lie down on them. Many Scottish plants with inferior 

 ovaries have the outer surface of the receptacle-tube covered 

 closely with prickles (e.g., Carrot, Torilis, &c.) or small sharp 



