CAKILE. 



The species of the genus Cakile in North and Subtropical 

 America, have long been a puzzle to systematists, C. maritima, C. 

 aequalis and C. Americana with their forms, having been interchanged 

 and intersynonymized to a considerable extent, mostly on account of 

 the variance of the leaves in specimens from different localities. It was 

 not until after a discriminative study of the fruits and seeds in the 

 specimens of this herbarium, and those of the Cambridge, Missouri, 

 and New York Botanical Gardens, and the United States National 

 Museum, that I was able to satisfactorily place the species, which 

 now appear clearly defined. 



The species-generating-force in the genus seems to have been 

 the development of the fruit for disseminating the plants in, and 

 from, what in each instance has been their habitat. It appears evi- 

 dent from the separation of the articulations of the loment, of which 

 the upper becomes easily detached while the lower falls with great 

 difficulty, that the former is intended to be disseminated by water, 

 near which the plant always grows; while the latter is intended either 

 to be carried by birds, or to be sown by the plant in the environment 

 of the parent. This conclusion appears to be well substantiated in 

 regard, at least, to the upper articulation, by the fact of the greater 

 sponginess of its pericarp, which is well adapted for floating, and the 

 cylindrical or globose form of the articulation itself, which, with its 

 ready separation from the lower when ripe, by the wind, renders its 

 progress to the water easy of achievement. The evolution for float- 

 age seems to have reached its height in the new species growing 

 upon the Alacran Shoals, from which, on account of their very lim- 

 ited area, the plant seems to have appreciated the necessity of remov- 

 ing itself as speedily as possible, and is increasing the possibility of 

 reaching a better habitat, by a great development of spongy tissue in 

 the upper or floating articulation; while the lower articulation, with 

 the apparent appreciation of the fact that there are no seed-eating 

 birds on the islets, and very little room along the limited strand to 

 accommodate much increase in the number of plants, has become 

 reduced to little more than a swelling of the pedicel. 



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