216 botanical gazette. [ September 



Explanation of Plate XVII.— Fig. 1. Typical fusiform spore. 

 Fig. 2. Typical clavate spore. 



Fig. 3. Thick-walled clavate spore of the form found on very out- 

 side of the spore mass. 



Fig. 4. Showing normal method of germination. 



Fig. 5. Method of germination of spores in an excess of water. 



Fig. 6. Method of germination of spores when damp. 



Fig. 7. Simplified method of same. 



Fig. 8. Fusiform spore germinating by the end. 



Fig. 9. Clavate spore germinating in a similar manner. 



Fig. 10. Terminal germination brought about by same conditions as 



in 6 and 7. 



All these figures are magnified 410 diam. and then reduced one- third , 



except Fig. 5, which is magnified 250 diam. 



Cryptogamic Laboratory of Harvard University. 



Observations on the temperature of trees 



H. L. RUSSELL. 



(with plate xviii.) 



During the winter and spring of 1889 experiments were 

 conducted upon the temperatures of trees, and the following 

 preliminary notice of some of the results obtained is given. 

 A number of questions have arisen in the course of the ex- 

 periments w 7 hich will require some time to solve, and as 

 these will have to be postponed till the next winter, it is 

 thought best to lay the facts gained so far before those inter- 

 ested in these problems, and reserve the remainder tor 

 further consideration. As far as could be ascertained very 

 few data have been collected upon the subject, and the 

 observations are recorded, as they may possibly be of use in 

 the future- 



The experiments were conducted in the following man- 

 ner: Holes one-half inch in diameter were bored into the 

 trees at equal heights from the ground. The thermometers 

 used were Centigrade, and were carefully compared with 

 each other to detect any variation in graduation. The ther- 

 mometers were inserted in the borings so that the base of 

 the bulb came in contact with the wood ; the space about the 

 thermometer being packed tightly with cotton- wool. 



