122 SUMMER 



The formation of the disc-flowers also gives them a solid 

 advantage in the struggle for sun and light. Each disc is 

 large and dense enough to cast a shade on competing stems 

 beneath it, and to divert them in the upward quest for the 

 sun. Growing shoots do not try to penetrate the federation 

 of tented umbels formed by a lusty hemlock-plant. They 

 either go round another way, or simply wither. The hem- 

 lock or the cow-parsnip provides the most perfect develop- 

 ment of the composite principle of blossom. The heads of 

 bloom are more symmetrical than those of the elder or the 

 mountain-ash or dogwood, and the same regular principle is 

 carried down through branchlets and main stem to the root. 

 The whole structure of the umbellifers is designed to support 

 as many of the flowering umbels as possible in the full eye 

 of the sun, and the umbels contrive in the same way to 

 expose as many lesser clusters of blossom. A simple umbel 

 is a cluster like that of the ivy, in which the blossoms and 

 berries spring on single stalks branching from the same 

 point of the flower-stem. The drawback to this plan is that 

 a cluster, to be compact, must be small ; for if the radiating 

 stalks were long enough to form a large cluster, they would 

 be too weak to stand hard usage from the weather. The 

 compound umbel is the typical pattern in the umbelliferous 

 tribe of hemlocks and their kin ; and this is an ingenious 

 development, providing strength as well as area. Each of 

 the main stems radiates again into a second whorl, and the 

 composite mosaic of the disc is supported on this series of 

 secondary stems. The downward structure of the plant is 

 almost equally symmetrical, till it terminates in the main 

 stalk and twisted root. The canelike strength of the 

 hollow hemlock or cow-parsnip stem can be best judged in 

 winter, when it is dead and leafless, and stands waiting to be 

 plucked by the hedgerow. It is no longer surprising that 



