I02 THE PLANT WORLD 



material, and by using a gloss finish the brittleness is over- 

 come and great strength is secured. 



The drying process is the most tedious of all.' As much 

 water as possible is first pressed from the sheet, after which 

 it may be hung up to dry, or dried by artificial heat. When 

 dry the leather is white or tan, and may be stained any color 

 desired. '*^- 



Leather may also be made from the leav^es of the 

 opuntia, the older joints only being used for the purpose. 



The covering of spines and epidermis are removed, leav- 

 ing the tough, wirelike fiber which grows just inside the outer 

 covering. A sheet is placed in the tanning bath for two 

 hours or more, then removed and dried. A remarkable 

 feature in this instance, is the fact that nature's coloring is 

 preserved in the leather if properly tanned. 



In conclusion — many small articles may be made from 

 the heart of the sahuaro, such as baskets, boxes, picture- 

 frames and numerous other objects of use and decoration. 



The entire trunk of this giant which reaches a height of 

 40 to 75 feet and a maximum diameter of two feet, may be 

 utilized in the manner described, and, as the sahuaro covers 

 an area of 120,000 square miles in Arizona and Sonora, no 

 lack of raw material will be encountered in the application 

 of this method of preparation. 



Tucson, Arizona, March 9, 1908. 



PERIODICITY IN THE FRUITING OF 

 A MARINE ALGA. 



W. D. HovT. 



Dictyota dichotomy is a brown alga with a flat, 

 forked, ribbon-like thallus common on portions of our coast 

 from North Carolina to Florida (Fig. 4.) It bears three 

 kinds of reproductive bodies — tetraspores (asexual) and 

 eggs and spermatozoids (sexual) — each plant bearing only 



