SHELDON: KOEBERLINIA SPINOSA. 105 



Strength attained by : 



1. Extreme lignification. 



2. Long splicing of bast. 



3. Long splicing of large tracheids. 



4. Heavy zone of stone cells firmly adhering to bast. 

 Supply of air provided for by intercellular spaces in : 



Epidermis. 

 Palisade. 

 Sponge. 

 Medullary ray. 

 Pith. 



On the whole, this plant presents a wonderful array of 

 "aids" to getting on in the desert. No other plant examined 

 showed so thick an epidermis and such an aerating system. A 

 few were almost leafless, a few had a heavy epidermis, some 

 were strongly lignified, others showed resinous secretions. Al- 

 most all had larger water-conducting vessels. With all the 

 adaptations that this plant had it seemed strange that it was 

 so rare, but upon investigation we find that by abortion the 

 many seeds are reduced to one, two or three to a berry. We 

 have not yet found out whether the berry is eaten by animals 

 or not. 



Tables of measurement, rainfall and evaporation are pre- 

 sented for reference ; also, a very superficial table giving some 

 facts in regard to a few other desert plants. I am indebted 

 to Mr. Peace for the tables on rainfall and evaporation. He 

 has also kindly furnished the two photographs as well as much 

 valuable information. Thanks are due to Doctor Trelease, 

 Doctor Land and Doctor Spalding, for kindness in answering 

 inquiries. I also wish to thank Doctor Billings for sugges- 

 tions, and Professor Stevens especially for ever-ready assist- 

 ance. It is a pleasure here to express gratitude to Doctor Mac- 

 Dougal for freely granting the facilities of the desert labora- 

 tory while the materials were being collected. 



