THE AMERICAN BOTANIST 57 



two or more buds showing a tendency to grow and in some 

 cases the bud's produce twigs two or three inches long the 

 first year. Clearly such buds are not to be classed with the 

 buds that occur alongside of the lateral buds, and our botani- 

 cal texts need a little revision at this point. There does not 

 seem to be a very definite idea as to just how much the pro- 

 duction of a'dventitious buds enters into this problem of extra 

 buds at the nodes. If one searches the plants of the world 

 he will be surprised to find buds appearing almost anywhere. 

 Many of these, in fact all that appear at the nodes, are re- 

 garded as accessory biids, but who shall say that this view is 

 correct. 



Fall of the Leaf. — It is pretty well known that leaver 

 'do not fall because of the frost though the approach of a cold 

 season may he responsible for their being cast off by the 

 parent plants. As a matter of fact, many plants never cast 

 their leaves. Mosses, ferns, and the great majority of 

 monocotyledons such as palms and lilies, do not throw off 

 their leaves. When these structures have served their pur- 

 pose, they wither and droop but remain attached to the plant 

 until decay or the play of the elements have detached them. 

 Most flowering plants however, long before autumn, begin to 

 make preparation for separating the leaves from the twigs. 

 This is accomplishd by a "cleavage plane" so-called, which 

 consists of a layer of brittle cells that grows across the petiole 

 and at the proper time causes it to fall. Before this layer of 

 cells is formed the plant forms a layer of cork cells just be- 

 low the place where it is to form. This often begins as early 

 as June and is manifestly of service in keeping the moisture 

 within the plant when the leaves have fallen. There are two 

 or three layers of cells in the tissue that cuts the leaf off and 

 this begins its growth at the epidemis and gradually spreads 

 across the petiole. Last of all the ends of the vessels carry- 

 ing water to the leaf are plugged with cork, and' the plant is 

 ready to enter the leafless condition. 



