26 



the same end is well known. Dr. Hooker describes the course of the 

 principal oceanic currents by which many of the Galapageian plants 

 have probably been conveyed tc their present localities ; and con- 

 cludes this part of his essay by showing the adaptation of the seeds 

 of several plants for transportation, arranged under their natural 

 orders, as follows : — 



" Menispermea. — Cissampelos presents a hard inner coat of the 

 pericarp- Albumen scanty, fleshy. 



" Crucifera. — Senebiera didyma, the only Galapageian species, 

 forms an exception to the general rule, that the plants of this 

 order are impatient of transport from the oily nature of their 

 cotyledons ; it is, as DeCandolle remarks, probably a native 

 of Buenos Ayres, whence it has been diffused over nearly all 

 the globe, and is continuing to spread. 



" Curvembryosce. — An artificial group, sufficiently natural, however, 

 for the present purpose. Seeds very minute in some, as Dry- 

 maria and Mollugo. The Chenopodege, Phytolacceae and 

 Portulaceae have a constitutional predilection to salt water. 

 Albumen farinaceous in the greater part of the Galapageian 

 genera. 



" Malvaceae. — Indurated pericarp of many. The floral envelopes 

 of Malachra are well adapted to stick to various means of 

 transport. 



" SapindacecB. — Crustaceous testa and exalbuminous seed of Car- 

 diospermum. 



" Zijgopliyllece. — Tribulus cistoides offers singular advantages for 

 transportation in its woody seed-vessels, their spines beset 

 with reversed prickles, and exalbuminous seeds. 



" Xamtkoxylea. — Osseous testa of Xanthoxylum. 



" Simarubece. — Castela has a crustaceous endocarp and scanty al- 

 bumen. 



" LeguminoscB. — Generally firm testa, exalbuminous seeds, and 

 great power of some to retain vitality. 



"Rubiacea. — The densely corneous albumen of many may afford a 

 sufficient protection to the seed. 



" Umbelliferce. — Helosciadium laciniatum is one of the few species 

 enjoying a wide range, for which I can offer no explanation. 



" Composite. — Exalbuminous seed. Pappus of Baccharis and ad- 

 hesive pubescence of Siegesbeckia orientalis. 



" Lobeliacece and Scrophularina. — Very minute seeds of Scoparia 

 dulcis and Lobelia Xalapensis. 



