60 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



seed as in the carcerulus of dead-nettle {Lamium), 

 This class of schizocarps includes the cremocarp of 

 Umbelliferse and the regma of Geraniaceae. In the 

 latter the fruit has a long beak or carpophore, to 

 which the one-seeded carpels adhere. When ripe 

 the carpels separate by their bases from the carpo- 

 phore and spring apart. At the same moment they 

 dehisce along their inner edges, and by the sudden- 

 ness of the movement the seeds are shot out to a 

 distance of several feet. Some species have the 

 carpels, or rather mericarps, indehiscent, in which 

 case the carpel itself and not the seed is the body 

 projected. This happens in the stork's-bill (Erodium), 

 belonging to this order. The fruit of Erodium is 

 perhaps the most interesting of all the hygroscopic 

 class. When it springs away from the carpophore 

 in the manner just described, the carpel of Erodiuin 

 is seen to have a loug slender filament at its apex 

 which is in the act of curling upon itself. After the 

 carpel alights, its awn continues to curve and twist 

 for a minute or two, until at last it has acquired the 

 cork-screw form and comes to rest. As long as the 

 awn is kept dry it does not change, but if it be 

 moistened with a drop of water it immediately 

 begins to straighten out, and in the course of a 

 minute or two becomes quite straight. At the same 

 time two or three line bristles near the base of the 

 awn spread out and lift up the carpel so that its 

 sharp point is directed into the soil. If now, as was 

 in all probability the case, the upj^er extremity of the 

 awn had been pressing against some object which 

 afforded a point of resistance, the moistening, in 

 consequence of the untwisting and elongation of the 

 awn, would have caused the point of the carpel to 

 be forced downward into the earth. Should the 

 soil after a time get dry, the awn will once more 

 curl and assume its cork-screw condition ; but instead 

 of the seed being drawn up by this shortening of 

 the awn, the latter is drawn down, for the seed 

 holds on, its point being barbed like a harpoon. 



