52 THE AMERICAN BOTANIST. 



Extra-floral nectaries make an interesting of:>ject les- 

 son well suited for advanced nature study and for elemen- 

 tary botany. The subject is no less important because 

 the reason for the phenomenon is not so ver\- evident and 

 bscause the teacher is notable to give a conclusive answer 

 so easily. In winter one may readily obtain material for 

 study by sprouting sweet potatoes {Ipomoea batatas) in 

 a dish with moist sphagum and sawdust. The large 

 foliar glands of the first leaves secrete an abundance of 

 nectar .^/o/jn H. Schaffner in The Ohio Naturalist. 



THE CALIFORNIA BIG TREES. 



In 1900 Professor Dudley made an extensive study of 

 the California big trees. He obtained data by counting 

 the concentric rings of growth on the cross sections of the 

 felled trunks. The oldest tree that he examined began its 

 existence in 525 B. C. His most interesting discovery, 

 however, relates to the remarkable recuperative properties 

 of these gigantic trees. The trunk of one tree that he 

 studied w^as 2,171 years old. Here is its liistor\' as 

 detailed by Prof. Dudlej^ : 



"271 B. C, it began its existence. 



"The first year of the Christian era it was about four 

 feet in diameter above the base. 



"245 A. D., at 516 j^ears of age, occured a burning on 

 the trunk three feet wide. One hundred and five years 

 were occupied in covering this wound with new tissue. 

 For 1,196 years no further injuries were registered. 



"1441 A. D., at 1,712 years of age, the tree was 

 burned a second time in two long grooves one and two 

 feet wide, respectively. Each had its own system of re- 

 pair. 



"One hundred and thirt3'-nine years of growth fol- 

 low^ed, including the time occupied in covering the wounds. 



"1580 A. D., at 1,851 years of age, occured another 

 fire, causing a burn on the trunk tw^o feet w^ide, w^hich it 

 took fifty-six years to cover with new tissue. 



"Two hundred and seventeen years of growth followed 

 this bum. 



