126 Trans. Acad. Sci. of St. Louis. 



to save space. Cellulose is much more condensed than 

 starch, proteids or fats. 



Ecology of Mucilaginous Seeds. — That mucilage in the 

 seeds of many plants is of considerable use has been abun- 

 dantly proven. In many small cruciferous seeds, as in Lepid- 

 ium, Capsella, and Sisymbrium ^ where the outer walls of the 

 epidermis become mucilaginous, the seeds adhere to any 

 moist object. This must also be the function of mucilage of 

 the smaller seeds in Euphorbia^ as in E. glyptosperma, E. 

 maculata, and E. polygonifolia, where it is produced in con- 

 siderable quantity. 



The objection may be raised for large cruciferous and 

 Euphorbia seeds that they do not adhere very readily, because 

 of their size. In proportion to their size the quantity of muci- 

 lao-e in these larger seeds is much less than in the smaller, at 

 least so far as I have investigated the species of Euphorbia 

 represented in Gray's Manual (416) and the Cruciferae of 

 the same work (417). The larger seeds are disseminated in 

 other ways. The smaller seeds of Ruellia, with copious muci- 

 laginous spiricles, are as easily disseminated as the seeds of 

 Euphorbia. The mechanism for dispersal of seeds in Arceu- 

 thobium is well known. The seed when ejected is thrown sev- 

 eral feet, the viscid mucilage in which it is embedded causing 

 it to stick to the bark of a tree when brought in contact with it. 



Grlitter ( 353) has suggested that the mucilage hairs of Lyfh- 

 raceae are for the purpose of fastening the seed to the soil, 

 which is doubtless true to some extent for cruciferous seeds, 

 Salvia, Ruellia, and Euphorbia. Kohne (390) suggests that 

 the mucilage of the seeds of LytJiraceae renders them more 

 buoyant. In Nymphaea and Euryale the arillus becomes 

 mucilaginous and floats on the water. The mucilage of the 

 well known squirting cucumber becomes highly turgescent 

 because of its great affinity for water and when mature the 

 stalk separates from the plant and thus scatters the seed. It 

 is a little more difficult to explain the use of mucilage in the 

 cucumber as we now know it. It is not improbable that it 

 served a similar purpose at one time. The mucilage formed 

 in the cross layer of cells at the base of petioles, and the 

 consequent deliquescence, help to separate leaves from the 



