40 



mists that hang around the hills every morning in the winter and 

 spring-time. In this way these growths obtain moisture enough 

 to enable them to reach maturity. Besides this the Atacaman 

 plants have acquired several peculiarities which admirably adapt 

 them to their conditions of life. One of these lies in the power 

 of the seeds to live for many years in the dry sand without ger- 

 minating. They have been known to retain their vitality for ten 

 years and then to sprout at the touch of rain. 



I suspected from appearances that a special weather protection 

 existed in many or all of these seeds, and Dr. Gregory of Barnard 

 College, who has, at my request, kindly examined microscopic sec- 

 tions of a number of species, confirms my suspicions so far as these 

 particular species are concerned. The seeds in every case proved 

 to have unusually thick walls and a copious supply of albumen 

 around the embryo. In one instance {Pintod) she reports that the 

 " seed coats are heavy, the outer one having peculiar shaped cells 

 which turn to mucilage on coming into contact with water." An- 

 other (a Tristagjna) has " copious albumen and the outer walls 

 are thickened and turned in color to a dark brown, making an ex- 

 tremely hard coat." Calandrinia seeds presented a coating 

 " somewhat heavy, but with a peculiar readiness to break on con- 

 tact with water." Cristaria has an integument of several layers 

 which together make a thick wall, and the interior albuminous. 

 Viola shows in the seed coat a contrivance similar to that of Pin- 

 toa, with more or less of albumen in the interior. 



While seeds are thus fortified against a protracted drought, 

 tubers and bulbs are equally well equipped by the large amount 

 of water or milk which they store up. I found many of the bulbs 

 that I collected so full of juice that I could squeeze it out in a 

 stream by hand. 



Another peculiarity of the herbaceous flora, evidently ac- 

 quired, is the early age at which the plants begin to flower and 

 fructify. As if aware that they have only an ephemeral life and 

 that what they have to do must be done quickly, they are scarcely 

 above ground before they put forth blossoms. Many species 

 may be seen in flower when hardly an inch in height, and which 

 go on flowering until they reach the stature of two or three feet — 

 if they can survive so long. I was continually deceived by this 



