NORTH AMERICAN GERANIACEAE. 



83 



ness. Supposing the basal point of the carpel to be slightly caught in the soil, which 

 readily happens eithei- as the fruit falls or when its movements begin, its withdrawal is 

 rendered difficult by the stiff ascending hairs with which the ovary is clothed; so that 

 while the crowding of the awn against bits of stubble, pebbles, or whatever small ob- 

 jects it may chance to have fallen among, tends to press the fruit farther into the earth 

 with every movement, whether the result of moistening or drying of the awn, the proba- 

 bility of its withdrawal, when once caught, is small. In some experiments performed in 

 my laboratory several years since, by Mr. E. II. Parker, it was observed that after the 

 fruit had been buried in damp soil for a few days, the awn softened at its base, so that 

 a pull, which otherwise might have withdrawn the fruit, merely broke away the awn, 



Fi-uit of Erodium glaucophyllum, X 2. 



thus removing the only source of danger to the self-planted seed, a provision which was 

 also noticed in Stipa, and has been recorded for these genera by Roux and Darwin 

 respectively. 



The contrivances in the fruit, therefore, are of a double nature, referring not only to 

 its removal from the parent plant, but to its insertion in the soil when a suitable point 

 has been reached. It is intei'esting to note that similar provisions are met with in widely 

 separated genera {Anemo7ie § Pahatilla, and species of Stipa and Aristidci) , not at all 

 related to Erodium; as well as in Pelargonium, a genus which stands very near the lat- 

 ter, the fruit of which is less elastic, and consequently more dependent upon the wind 

 for dissemination, although it is ultimately planted in the same manner. 



