1 124 Home Nature-Study Course. 



(7). What insects do you most often see visiting thistle blossoms 

 for pollen or nectar? 



(8). Are the flower-heads protected by prickly bracts or leaves? 



(9). Carefully strip away the bracts from the side of the flower-head 

 and note how the seeds are placed on the receptacle at the base of the 

 blossom. If you have time and patience for the task, count the number 

 of seeds in one head. 



(10). Remove one of the little green seeds and study with a lens 

 the floret that is attached to it. What is the shape of the colored part 

 of the floret? By what is it surrounded? 



(11). Can you see any other parts of the flower within the purple 

 tube? 



(12). Is the protruding tip of the pistil divided or sub-shaped? 



(13). Where are the anthers or pollen-boxes and how do they shed 

 their pollen? What color is the pollen? 



(14). Chew the thistle blossom at the base of the tubes? Is it pleasant 

 or disagreeable to the taste? 



Facts for Teachers. — The flowers of these thistles are purple in color and very 

 fragrant ; those of the Common Thistle grow in single heads at the summit of the 

 stalk and in the axils of the upper leaves, but the Canada flings out several loosely 

 branching clusters of bloom from the same places. The topmost heads open first, 

 proceeding in succession down tlie stalk ; of the individual flowers in the head, 

 those in the outer rows first mature aiAi protrude their pistils; the pollen grains 

 are white. 



The numerous blossoms of the Canada Thistle are small, being about a half- 

 inch in diameter, while the Lance-leaf's flower-head measures about an inch and 

 a half across. This plant is often called the Bull Thistle, but that name has been 

 given and should be restricted to the big Cirsinm pumilium, the most fragrant and 

 largest flowered thistle of all, whose lilac or magenta heads are often three inches 

 broad. It is less common than the Lance-leaf and can be told from it by its solid 

 tap-root ; its low, stout stalk ; its broader leaves and its spines, which are shorter 

 and less fierce ; around the flower-head the bracts are slightly sticky to make up 

 for the weakness of the prickles. But the bracts surrounding the Common Thistle's 

 blossoms have spines as sharp as needles. Those on the Canada's flowers have no 

 spines at all and even the stem below the flower-head is free from prickles. 



Thistles belong to the Composite Family of plants which seems to have found 

 that in union is strength. Each thistle-head is a community of perfect flowers. 

 Stripping away the protecting bracts and separating a flower from the company, 

 one finds that the purple corolla is tube-shaped parting into five fringy lobes 

 at the top and fading to white at its nectar-filled base. Its calyx takes the form 

 of fine white silken hairs, called a pappus. The five stamens are inserted on the 

 corolla and the anthers are united in a tube, within which their pollen is dis- 

 charged. The pistil, ripening later, shoves out the pollen with its tip which at 

 first is blunt at the end, its two-parted lips so tightly held together that not a 

 grain of its own flower's pollen can touch them ; but when thrust far out beyond 



