1 882.] On the Compass Plant. 633 



non, it is unnecessary to search for another. And this brings me 

 to refer to the admirable drawing of the transverse section of the 

 leaf, magnified 235 times, of Si// given on page 



157 of Botany by C. E. Bessey, professor of botany in the Iowa 

 Agricultural College. He says, " Its chlorophyll-bearing paren- 

 chyma is almost entirely arranged as palisade tissue, so that the 

 upper and lower portions are almost exactly identical in struc- 

 ture ;" on page 103 he says, " there are in the true upper surface 

 52,700 stomata per square inch, and on the under surface 57,300 

 per square inch." 



This magnifying of a section of the leaf is a dissection, and 

 thus there is no cause to suppose the existence of any spiral 

 ducts such as are above referred to. Professor Bessey, living in 

 the prairie region has the best possible opportunities to observe 

 the compass plant. He says, page 515: "Its large pinnately 

 lobed leaves twist upon their petioles, so as to present one surface 

 of the blade to the east and the other to the west, the two edges 

 being upon the meridian." This language applies to the leaves 

 of the flowering plant, for in the growing of the radical leaf there 

 is no. cause for the twisting of the petiole in order that it may 

 assume its meridional position. 



As to the history of the plant in Europe. The following is an 

 extract from the article by Sir Joseph Hooker in the London 

 Botanical Magazine for January, 1881, above quoted, which is 

 preceded by a drawing of the flowering plant: 



"This noble plant was introduced into Europe in 1781 by 

 Thouin and flowered for the first time in the Botanical Garden 

 of Upsala in Sweden. It has been in cultivation in Europe ever 

 since, though its name and fame as the compass plant of the 

 prauics are of comparatively modern date, it having before that 

 borne the popular names of turpentine plant *nd rosin weed, ex- 

 cept among the hunters and settlers in the Western Sta' With 

 regard to the history of its reputed properties as an indicator of 

 the meridian by the position of its leaves, I am fortunate in hav- 

 ing recourse to my friend Professor Asa Gray, now in England, 

 who has most kindly furnished me the following very interesting 

 account of this matter : 



The first announcement of the tendency of the leaves of the 

 compass plant to direct their edges to the north and south, was 

 made by General (then Lieutenant) Alvord of the U. S. Army, in 

 the year 1842, and again in 1849, in communications to the Amer- 

 ican Association for the Ad\ incement of Science. But the fact 

 appears to have long been familiar to the hunters who traversed 



