2l8 



Minnesota Plant Life. 



the power of the purple substances in the spathe, together with 

 the respiratory activity of the fleshy spike, to increase the tem- 

 perature. In the jack-in- 

 the-pulpit flower the pecu- 

 liar little club-shaped sterile 

 end of the spike is probably 

 a respiratory organ and to- 

 gether with the special col- 

 oring substances does its 

 part in raising the tempera- 

 ture. Small insects learn 

 that these flower clusters 

 offer them comfortable 

 shelter and seek them, and 

 as a result pollination is se- 

 cured. The flowers of most 

 of the arums depend upon 

 this ability to furnish heat 

 rather than upon perfumes, 

 gaudy colors or the secre- 

 tion of nectar to attract 

 their insect visitors. 



Burrowing bulbs. An- 

 other curious feature in the 

 lives of many arums is the 

 burrowing habit of the 

 young bulbs. If a flower 

 pot about six inches tall is 

 filled with rich loam and 

 some seeds of the skunk- 

 cabbage or jack-in-the-pul- 

 pit are planted about half 

 an inch below the surface 

 and permitted to germinate, 

 the plantlets when they 

 burst forth will at once be- 

 gin the formation of bulbs 

 by expanding the lower 

 portions of their stems into 



FIG. 97. A skunk-cabbage in early spring, be- 

 fore the leaves have unfolded. The purple 

 hood covering the flower cluster is shown on 

 one side. After Atkinson. 



