288 ADDITIONAL SPECIES. 



case they must perish. On the dry land they are useless, 

 for it is a water plant ; and, on the other hand, if blown to 

 the deeper parts, they will sink to the bottom, and never 

 germinate, or germinate in vain. Now, though these seeds 

 are exposed to so many dangers, and though the continu- 

 ance of the species depends on their preservation, yet is 

 their number by no means great. The flower-heads are 

 small, and never numerous ; the seeds large in proportion, 

 and, of course, few are produced by a single plant. This 

 apparent deficiency is, however, well compensated by a 

 peculiar provision. The seeds are four-cornered, and the 

 corners are furnished with sharp deflexed prickles. Each 

 of these corners is also prolonged into an awn still more 

 thickly set with prickles than the corner itself. Now, the 

 intention of this conformation is obvious. The seed falls 

 with the awns pointing upwards, the prickles come into 

 action, attach themselves to the various plants which float 

 at or near the surface, and, becoming fixed, germinate in 

 a favourable situation ; for as the deflexed prickles fix to 

 the first objects which they meet, the seeds are kept as 

 near as possible to the stations of the old plants, and pre- 

 vented from being carried either on shore or into places 

 that are too deep. How well the prickles are fitted to 

 perform their office may be gathered from a fact men- 

 tioned by LIGHTFOOT, that " the seeds of the Bidens tri- 

 partita have been known sometimes to destroy the Cypri- 

 nus auratus or goldfinch, by adhering to their gills or jaws." 

 So closely do they attach themselves to whatever they 

 come in contact with ! May not this structure of theirs 

 also save them from the depredations of birds ? 



ORCHIS, (p. 190.) 



(5. O. viridis, knobs tapering, clustered, divided ; lip of the nec- 

 tary linear, with 3 teeth, the middle one smallest ; spur very 

 short, slightly cloven. (3 to 6 inches high ; flowers greenish.) 

 Frog Orchis. 



Hab> Heathy pastures. Amongst some natural wood op- 

 posite the village of Lon'gformacus, in the west of Ber- 

 wickshire ; and on Doddington Moor, North Durham. 

 July Sept. 7J. 



In both of the above stations a solitary specimen only could 

 be found after a very diligent search, a fact perhaps worth 

 mentioning, because O. viridis in this respect differs from 

 all our other species, which are social or gregarious plants. 



