THE AMERICAN BOTANIST 51 



plants as Solomon's seal, tulips, hyacinths and the like have 

 only roots of this kind. It is also easily shown that at the be- 

 ginning of their second 5^ear, most plants with large tap roots 

 develop a large number of adventitious roots on all sides of the 

 main root. Potato and artichoke tubers also begin their 

 growth in spring by putting out numerous roots of this kind. 



Cork. — As most people know, cork is the outer bark of 

 an oak. This tree, known to the botanists as Quercus suber, is 

 an evergreen, native to the Mediterranean region, and is cul- 

 tivated in France, Spain, Portugal, Italy, Morocco, Tunis and 

 Algiers. If carefully done, removing the bark does not injure 

 the tree, and a new supply may be obtained from the same 

 specimen after a few years. We are so familiar with the use 

 of cork for the stoppers of bottles that we seldom realize its 

 manifold other uses, though its connection with bottles dates 

 back only about five 'hundred years. We so commonly speak 

 of the stopper of a bottle as a cork, that we see no incongruity 

 in the expression "a rubber cork." Just as our word for stop- 

 per has been derived from the word cork, so cork itself has 

 probably been derived from the Spanish corcho which in turn 

 is derived from the Latin cortex meaning rind. Some authors, 

 however would derive cork from Quercus the generic name of 

 all oaks. Cork is present in the bark of all trees though in 

 quantities too small to make it useful in the many ways in 

 which cork from the cork oak is employed. The cork-barked 

 elm, the sweet gum and a few others have strongly developed 

 cork. 



Dog-bane Rubber. — The rubber of commerce is the pro- 

 duct of a number of tropical trees and vines which belong to 

 several different families of plants. All contain a sticky juice 

 called latex from which the rubber is obtained. Several of 

 these plant families are represented in more northern floras 

 and like their tropical relatives are characterized by the pos- 

 session of latex. The fact that exotic species of the Apocy- 

 naceae or dog-bane family, especially Hancornia, Landolphia 



