268 7 lie Scottish Natutalist. 



is met with in one or two plants allied to the cucumber — viz., 

 Elaterium, or " squirting cucumber." The fruit is a fleshy oval 

 body with elastic walls in a constant state of tension. The seeds 

 lie imbedded in a mass of pulp in its interior. When they are 

 ripe the fruit drops off its stalk, leaving an opening at the point 

 of attachment, and through this opening the seeds and pulp are 

 shot out to a distance of several feet by the sudden contraction 

 of the elastic walls. Of this kind of dehiscence we have no ex- 

 ample among native plants, and I must apologise for digressing 

 to mention it. 



Lastly, we find among grasses some in which the fruits are 

 able to move over the surface of the ground, or even to burrow 

 into it to sufficient depth to cover themselves. These move- 

 ments result from the nature of the awns, which remain attached 

 to the glumes or bracts, which break away and remain as a 

 covering to the ovary. The awns are bent or twisted, and have 

 the peculiarity of being very ready to absorb or to give off 

 moisture, the bend or spiral altering its dimensions with every 

 variation in the amount of moisture. Every such change of 

 position moves the ovary, but, owing to fine prominences on 

 the glumes, &c, they can move only in one direction; — thus 

 every movement propels it forward, and in this way the seeds 

 may be pretty widely distributed after some time. 



As formerly mentioned, frequently the same methods of dis- 

 tribution are found in plants wide apart in structure, while in 

 other plants nearly allied to one another, the methods are very 

 distinct, the adaptations being suited to very different agencies. 

 And you will probably readily understand that such resem- 

 blances are no proof of genetic relationship, and such differ- 

 ences no proof of distance apart, but that they depend on 

 environment, and on the conditions best suited for the welfare 

 of the various species of plants. Though this paper is already 

 a long one, I may perhaps be permitted to instance more fully 

 a few examples of resemblances and of differences in this view. 

 Of resemblances we meet with the elongated plumose style, 

 serving as a float, in Clematis and in Anemone Pulsatilla among 

 Ranimculacece. ; and again in Dry as octopetala and Geum mon- 

 tanum among Rosacece. Seeds with an unilateral wing occur in 

 Coniferce (firs, &c), in the mahogany tree (Swiete?iia), in Pro- 

 teacece (Banksia, &c), and various others ; seeds surrounded 

 with a wing in Bigfioniacece, Caryoft/iyllacece (Spergi/laria, Dian- 

 t/uts, &c.), Crueifercc (Alyssum, &c), Liliacecz, (Liliwn, &c), 



