Vol. I] STEWART— BOTANY OF THE GALAPAGOS ISLANDS 217 



The Rhizophoraceae and Comhretaceae include some of the 

 most important elements of the littoral vegetation. Rhizophora 

 Mangle of the first of these families forms dense low forests 

 below high tide mark, while Conocarpus erectus and Laguncu- 

 laria racemosa of the second occur farther back as bushes and 

 small trees. 



The various species of Ipomoea are the most significant 

 members of the Convolvulaceae in that some of the most im- 

 portant of the herbaceous lianes of the islands are members 

 of the genus. This genus also furnishes species which occur 

 under all conditions, halophytic, xerophytic, and mesophytic. 



The Boraginaceae furnish some noteworthy elements of the 

 flora in all of the regions. The various species of Cordia con- 

 stitute important factors of the flora in the dry and transition 

 regions, while the species of Tournefortia provide some of the 

 most common bushes in all of the regions, especially in the 

 moist and grassy. 



Avicennia, Clerodendron, and Lantana are the three genera 

 of the Verbenaceae which are of prime importance. Avicennia 

 oificinalis forms an important element of the littoral vegetation 

 in the form of low forest trees, while the two remaining genera 

 furnish some of the most characteristic bushes of the dry and 

 transition regions. 



The Solanaceae are the eighth largest family in number of 

 species on the islands, but are of rather secondary importance, 

 as the species for the most part are herbaceous and not espe- 

 cially abundant in any of the regions except during the spring 

 season. At that time they furnish several of the common 

 weeds. 



The Ruhiaceae stand next in importance to the Solanaceae 

 in number of species, but most of these are relatively small in 

 size. This is one of the most important families represented in 

 the archipelago in that it contains common species in all of the 

 regions. The various species of Borreria are very frequent in 

 the dry regions, some of them inhabiting the most desert situa- 

 tions, even to the exclusion of almost all other species of plants. 

 Bushes of Chiococca alba often form an important element of 

 the flora in the transition regions, and Psycho tria ruHpes is of 

 prime importance in the Scalesia forests in the moist regions, 

 where it is one of the most abundant bushes. 



