42 INVASION 



the degree of mobility as a rule is very high. All exhibit in 

 common the development of hooks or barbs, by which they 

 are disseminated in consequence of attachment, though the 

 number, size and disposition of the hooks vary exceedingly. 



10. Viscid, gloeospores ( Oloeosporae,\ yXoios, o, a sticky, 

 clammy stuff). In these, the inflorescence is more or less 

 covered with a viscid substance, as in species of Silene, or 

 the fruit is beset with glandular hairs, as in Cerastium, 

 Salvia, etc. 



11. Fleshy, sarcospores (Sarcosporae, <Ta.pt, a-apKO's, ^, flesh, 

 pulp of fruit). These are intended for dissemination by 

 deglutition, largely by birds; the effectiveness of the modifi- 

 cation depends in a large degree upon the resistance of the 

 seed envelope to digestion. The mobility varies greatly, 

 but the area over which migration may be effected is large. 



12. Nut-fruited, creatospores (Creatosporae, Kpeas, aTos, to, 

 meat). This group includes those plants with nut fruits, 

 which are carried away and secreted by animals for food. 



18. Flagellate, mastigospores {Mastigosporae, pAcrr^, syos, v, 

 lash). These are plants with ciliate or flagellate propa- 

 gative cells, i.e. zoogonidia, as in Protococcus, Ulothrix, 

 Oedogoninm, Ectocarpus, etc., or with plant bodies similarly 

 motile, Bacteriaceae and Volvocaceae. 



The position on the plant of the organ to be disseminated, 

 i.e., its exposure to the distributing agent, plays a consider- 

 able part in determining the degree of mobility. In the 

 majority of plants, the position of the inflorescence itself re- 

 sults in maximum exposure, but in a large number of forms 

 special modifications have been developed for placing the 

 spores or seeds in a more favorable position. In both cases, 

 there are often present also devices for bringing about the 

 abscission of the seed or fruit. It is moreover self-evident 

 that the height of the infiorescence above ground or above 

 the surrounding vegetation is likewise of considerable im- 

 portance in increasing the trajectory. It is yet too early 

 to make a complete classification of contrivances for 

 placing disseminules in the most favorable exposure, but the 

 following will serve as a basis for future arrangements. 



