214 THE FORMATION 



7. Awned, acospores. These are almost exclusively grasses, in which the 

 awns serve for distribution by wind, water, or animals, and even, according 

 to Kemer. by hygroscopic creeping movements. The mobility in many cases 

 is great. 



8. Spiny, centrospores. This group contains a few representatives which 

 possess a moderate degree of mobility by attachment, as in Tribulus and 

 Cenchrus. 



9. Hooked, oncospores. The members of this group are extremely numer- 

 ous, and the degree of mobility as a rule is very high. All exhibit in com- 

 mon 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. In these, the inflorescence is more or less covered 

 with a viscid substance, as in species of Silcne, or the fruit is beset with 

 glandular hairs, as in Cerastmm, Salvia, etc. 



11. Fleshy, sarcosporcs. These are intended for dissemination by deglu- 

 tition, largely by birds; the eflfectiveness of the modification 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. This group includes those plants with nut 

 fruits which are carried away and secreted by animals for food. 



13. Flagellate, mastigospores. These are plants with ciliate or flagellate 

 propagative cells, i. e., zoogonidia, as in Protococciis, Ulothrix, Ocdogonium, 

 Ectocarpus, etc., or with plant bodies similarly motile, Bacteriaceae and 

 Volvo caceae. 



265. Position of disseminule. The position on the plant of the organ to 

 be disseminated, i. e., its exposure to the distributing agent, plays a consid- 

 erable part in determming the degree of mobility. In the majority of plants, 

 the position of the inflorescence itself results in maximum exposure, but in a 

 large num'ber 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 inflorescence 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 disscminulcs in the most favorable 

 exposure, but the following will serve as a basis for future arrangements. 



I. In all operculate Discomycctcs, and especially in the Ascoholaccae, 

 where the asci project above the hymenium, the spores arc raised above the 



