THE AMERICAN BOTANIST 11 



from the end of the water tubes by a few intermediary cells. 

 The guard cells close the stomata in the dark and during the 

 night the accumulated water escapes through the open doors of 

 the water pores. Some plants, like the geranium, exude their 

 moisture through tiny hairs. The fungi exude from the gen- 

 eral surface. 



Exudation water differs in another respect from the water 

 of transpiration. Being in the liquid state, it carries with it 

 many of the plant foods in solution and therefore has a compo- 

 sition similar to sap. As a general rule, the drops collect slowly, 

 yet from the tip of a leaf of Elephant's Ear, 25 drops have been 

 known to fall in one minute. 



From the young leaves of certain Aroids, the family to 

 which the Jack-in-the-pulpit belongs, water is sometimes ejected 

 in a fine spray to a distance of a few inches. Guttation is 

 especially common in shade plants that live in conditions which 

 do not favor transpiration. 



There is a certain kind of guttation which is commonly 

 called "bleeding". This is- the losing of sap due to cutting or 

 injury by man, such as improper pruning. In some cases this 

 bleeding is effected purposely, as in the case of the sugar maple 

 and the century plant. In the sugar maple, bleeding is resorted 

 to, to obtain the great commercial product, maple sugar. The 

 sap of the maple represents the surplus of the tree's winter 

 storage. In the warmth of early spring- the roots begin to 

 absorb large quantities of soil water. This dissolves the sugar 

 and both rise in the vessels. By tapping at this time large 

 quantities of sap may be extracted. This loss is not felt by the 

 trees because just at this time they are sending out leaves which 

 are able to manufacture their own food. 



Sugar making begins with the upward flow of the crude 

 sap in February or March and continues until the buds begin to 

 swell. Trees twenty or thirty years old are considered the most 



