DICOTYLEDONS: FA GALES. 



SUGGESTIONS FOR STUDY OF THE OAK. 



1161. The oak. (The white oak or any common one in the neighbor- 

 hood.) 



The leaves. Determine the arrangement of the leaves on the shoot. 

 Sketch a leaf showing the form, outline, and venation. Compare the 

 young leaves with the old ones as to texture, surface characters, etc. 



The inflorescence. What is the kind of inflorescence? Are both kinds 

 of flowers in the same inflorescence or in different inflorescences? 



The staminate inflorescence. Note the cluster of staminate aments. 

 Determine a single flower and sketch it to show the parts. What parts of 

 the flower are present ? Determine the number of parts of each set present. 



The pistillate inflorescence. How does it differ from the staminate in- 

 florescence? Sketch a pistillate flower, showing the parts. What parts 

 of the flower are present? 



The fruit (an acorn with the cup). Sketch an acorn in the "cup." 

 What is the homology of the cup i.e., to what part or series of members 

 of the plant does it belong? Could the pistillate flower of the ancestors 

 of the oak have been in the form of aments, and if so, could the cup of the 

 acorn represent the degraded and consolidated ament? If so, what part 

 of the ament would now be represented in the cup? (It has also been 

 suggested that the scales of the involucre which makes up the cup are 

 adventitious growths accompanying the development of the fruit.) See 

 Chapter XLIV. 



(If the acorn has not been studied under the paragraph dealing with 

 seeds and fruits, and if there is time now, remove the wall of the acorn 

 and determine the parts of the embryo. Are any parts of the embryo 

 green while still enclosed within the acorn?) 



Field observations on the oaks. Compare the time of appearance of the 

 flowers and leaves of the oak. What about the abundance of the pollen ? 

 How are the oaks pollinated ? The ament-bearing plants are usually wind- 

 pollinated, and for this reason there is an abundance of pollen, and always 

 in the form of dust. Is there an exception to this general rule? How 

 long after the flowers are formed before the acorn is ripe? 



If there is time during excursions, note other ament-bearing plants. 



Material. Mature leaves, leafy shoots, sprays of the flowers, both pis- 

 tillate and staminate; fruit (the acorn in the cups). 



