766 MINNESOTA BOTANICAL STUDIES. 



As mentioned above, the windward side of the range is a 

 precipice, but on the lee side the conditions are different. Here 

 numerous narrow ridges jut out, with deep valleys between. 

 The sides of these ridges are so steep, that they are entirely 

 inaccessible at most places. The lower ends, however, slope 

 gradually toward the sea, so that by following along the back- 

 bone, one can ascend to the main ridge, although this is ac- 

 complished only by great labor, difficulty, and danger, as a 

 misstep in some places would mean a plunge of 1,000 feet into 

 the valley below. 



The Waianae range extends along the shorter western coast. 

 Its highest point is flat- topped Mt. Kaala, which has an eleva- 

 tion of 4,000 feet, and is the highest point on the island. 



Although the subterranean fires were extinguished ages since 

 on this island, there is abundant evidence to show that there 

 once was great volcanic activity. There are four tufa cones in 

 the vicinity of Honolulu. A short distance west of the city is 

 the twin crater of Moanalua, containing a lake of salt water, 

 which does not appear to be connected with the ocean. Punch- 

 bowl stands like a sentinel on the northeastern edge of the city. 

 Diamond Head, the most imposing of the four, is four miles 

 east. It has a height of 700 feet. Four or five miles beyond, 

 near the extreme eastern end of the island, is Koko Head. A 

 short distance beyond Diamond Head, are the remains of an 

 ancient lava flow, where the immense black rocks are piled up 

 in picturesque confusion. Just opposite, on the heights of 

 Palolo, are the remains of a crater, and probably this flow 

 emonated from thence, although there is not much trace of it in 

 the intervening low ground. 



This open country, or "lowland zone," as Hillebrand calls 

 it, is almost rainless during the greater part of the year, and 

 has few native species. It is the home of introduced species, a 

 number of which are annuals, and spring up after the winter 

 rains. In the dry and dusty regions, both east and west of 

 Honolulu, the Algaroba tree, a species of Prosopis, nourishes, 

 as do also large numbers of Acacia famesiana, which here is 

 always a shrub. Opuntia tuna is a familiar figure of the land- 

 scape. Argemone mexicana has all the appearance of an intro- 

 duced plant, yet it must be a native, as it was found on the 

 Islands when Captain Cook first touched there. 



Lantana camara is perhaps the most noxious of all the intro- 

 duced plants. It has spread over all of the islands of the 

 group, and rendered useless mauy acres of pasture land. 



