104 KANSAS UNIVERSITY SCIENCE BULLETIN. 



protection for the ovules against the intense aridity of the des- 

 ert atmosphere. The mesophyll of the ovary is well supplied 

 with chorophyll bodies and contains numerous mucilage cells, 

 thus assisting in the provision for intensest drought. A resin- 

 ous gum is found in the seed vessel surrounding the ovules and 

 the vascular bundles in the placenta. (Figs. 1, 2, 3, 4, plate 

 XXIV.) The resinous gum is not found elsewhere. 



The contents of the cells of the stomata of the inner wall of 

 the seed vessel stain a deep blue with c. z. i., showing that the 

 guard cells here are living and filled with non-nitrogenous ma- 

 terial. 



The mucilage cells finally break down, thus forming large 

 mucilage reservoirs. (Figs. 8, 7, 5, plate XXIV.) 



CONCLUSION. 



Koeberlinia is what Clements would call a stem xerophyte. 

 The low stature of the plant, its compact habit of growth and 

 the heavily cutinized surface everywhere, reduces evaporation 

 to a minimum. The dead-air spaces furnished by the outer 

 stomatal chambers also contribute toward this end. A supply 

 of moisture is insured for the more strongly growing parts by 

 the storage of water in special reservoirs and by the presence 

 of mucilage in the seed vessel. The resinous gum aids in con- 

 serving moisture. Greater strength is secured, perhaps, 

 through the peculiar splicing of the large tracheids. The stone 

 cells, with their firm adherence to the bast fibers, also give 

 strength. The air spaces in epidermis, palisade tissue, sponge, 

 medullary rays and pith insure a goodly supply of CO2 without 

 much evaporation. These points might be summed up thus : 



Evaporation minimized by: 



1. Dispensing with leaves. 



2. Heavy cutinization on all exposed surfaces. 



3. Dead-airspaces (outer stomatal chambers). 



4. Low stature. 



5. Compact growth. 



6. Resinous gum surrounding tender growths. 



Moisture supply provided for by : 



1. Special reservoirs for water storage. 



2. Mucilage in cells in seed vessel. 



3. Tracheal elements. 



4. Presence of resinous gum. 



