1 88 SILPHIUM LACINIATUM. COMPASS PLANT. 



would necessarily result in the edge of the leaf being towards 

 the point of greatest light, that is, the meridian. There may be 

 something wrong with this light-abhorring theory ; at least, we 

 have only room here to say that many vertical-leaved plants have 

 the stomata on both surfaces, but show no polarity. 



In the " Proceedings of the Academy of Natural Sciences of 

 Philadelphia" for 1870, are some detailed facts about the growth 

 of the flowers in the compass plant, which show that growth or 

 the development of a plant is not one continuous process, but 

 proceeds by jerks, rhythms, or waves of varying intensities. 

 The large yellow ray petals close over the disc at night, com- 

 mencing to expand at 4 in the morning, and becoming horizontal 

 at 6.20. At 4 40 five of the fifteen spiral coils composing the 

 disc commence to grow. The tubular corollas complete their 

 growth by 5.20. The stamens and false pistil keep growing till 

 5.45, when the stamens stop — the pistil going on till 6.10. By 9 

 in the morning bees arrived, and the florets (which are barren) 

 fell under the touch of the insect, and in their fall fertilized the 

 pistils in the ray florets, which are the only flowers yielding seed. 



Its introduction to the notice of European botanists was prob- 

 ably through John Bartram. A letter of Collinson's to him, 

 dated December, 1763, says: "I can tell thee Gordon has raised 

 the fine, stately, broad-leaved Silphium ; but thee mentions three 

 fine species from New Virginia, by the Ohio ; but which of them 

 ours is I don't know ; but thy specimens will set us right," And 

 Linnaeus, in the second edidon of his " Species Plantarum," pub- 

 lished in the same year, says he derived his knowledge of the 

 plant from Collinson, who had it " from Mississippi." 



Explanations of the Plate.— i. Barren male or disc flower. 2. Scale or involucel from the 

 base of a disc floret. 3. A hair from the stem magnified. 4. Flower longitudinally 

 divided, showing (a) the receptacle, (b) the involucral scales, (c) the fertile ray floret with 

 akene and deeply divided pistil, (d) ray floret from a side view, and (e) barren disc floret. 

 5. Portion of stem, showing leaf and its insertion. 6. Upper portion of a flowering stem. 

 The whole from an Illinois specimen. 



