Minnesota Plant Life. 307 



illuminated. A plant placed in a window will within a short 

 time incline all its leaves so that their surfaces are perpendic- 

 ular to the rays of sunlight. If the pot is now turned around, 

 in a short time the leaves will slowly swing' back and accom- 

 modate themselves to the new direction from which the light 

 is shining. 



Prickly ashes. The rue family is represented in Minnesota 

 by two shrubs. One, the prickly ash, is abundant throughout 

 the southern part of the state, extending as far north as Leech 

 lake. The other, known as the three-leaved ash, three-leaved 

 elm or hop tree, is reputed to occur in southeastern Minnesota. 

 The prickly ashes sometimes grow into small trees. Their 

 leaves are alternate, resembling those of the common ash trees, 

 and there are from five to eleven leaflets in each leaf. The 

 flowers are borne in little clusters, appearing in the early spring 

 before the foliage, or while the leaves are beginning to emerge 

 from the buds. The flowers are green and of small size. They 

 mature into black, egg-shaped capsules, each containing one 

 or two black and glistening seeds. The twigs of this plant 

 are armed with thorns. Prickly ashes are common on hillsides, 

 along rivers and at the edges of oak woods. 



Three-leaved elms. The three-leaved elm has a fruit very 

 similar in appearance to that of the slippery elm, though the 

 plants are not particularly related to each other. The leaves 

 are made up of three leaflets, and the fruit has a decidedly bitter 

 taste, quite different from that of a true elm fruit. 



Milkworts. The polygala family produces some small herbs 

 known as polygalas, milkworts and snakeroots. The Seneca 

 snakeroot is gathered in quantities on account of the medicinal 

 value of the rootstock. These plants may be recognized by 

 their flowers, generally in racemes or spikes, but in some in- 

 stances becoming condensed into heads, and by the three petals 

 united into a tube which is deeply cleft on one side. Two of 

 the sepals are larger than the other three and there are usually 

 eight stamens. The fruit is a small capsule and the seeds have 

 peculiar appendages. 



Spurges. Fifteen species of spurges occur in Minnesota. 

 Most of them are mat-plants, forming disks of much branched 

 vegetation similar in appearance to the carpetweeds and purs- 



