87 



could have had no connection with the Calyptospora, How are we to ac- 

 count for the presence of the Calyptospora on a moderate sized Vaccinium 

 bush in a deep cedar swamp, if one of the necessary stages of its de- 

 velopment is Aecidiujji cohimnare} Here then we have three different 

 genera, including teleutosporic forms found both in Europe and this 

 country, and yet what is assumed in Europe to be the necessary 

 aecidial form is Avanting with us. But certainly we must assume 

 that, in matters of development, what is true of a fungus in one coun- 

 try must be true in another. In the present question, it will be ob- 

 served that the cumulative character of the evidence is of value. 



82. Abnormal Habit of Asc^epias amplexicaulis. 



By H, W. Ravenel. 

 About ten years ago, in a note to Prof. Gray (which he afterwards 

 presented with his comments at the meeting of the Atner. Assoc, for 

 Adv. of Science in Indianapolis, 1871*) I called his attention to the 

 seemingly one-ranked leaves of Baptisia perfoliata\ and traced the 

 cause of this anomaly to the peculiar attachment of the leaves to the 

 stem. I have lately observed the same thing in Asdepias ainplexi- 

 caulis — the only difference being that in the case of the lattef the 

 leaves are opposite — in the former, alternate. 



The habit of Asdepias amplexicaulis is to throw out several (2 or 

 3 to a dozen) stout stems from the roots, all diverging at once and 

 assuming a recumbent position. The stems are almost universally 

 unbranched, and the inflorescence occupies the axils of the upper 

 leaves. The stems being horizontally reclined, the leaves all assume 

 a vertical position, exposing both surfaces alike to the sun. 



The leaf arrangement is evidently distichous (phyllotaxis -1), and 

 the twisting of the stem, alternately from right to left and left to 

 right (the torsion taking place whilst the leaves are unfolding) brings 

 them ultimately to a double, one-ranked series. 



As in the case of Baptisia perfoliafa^ the alternate torsion of each 

 internode in opposite directions can be traced on the stem, but is more 

 clearly seen by stripping off a leaf with the adhering bark downward 

 from one node to the next, when it is seen to pass spirally through 

 half the diameter of the stem, from right to left and from left to right 

 alternately through its whole extent, the torsion being pretty uniform 

 through the internodal spaces. This alternate twisting in different 

 directions relieves the stem of a continuous torsion through its entire 

 axis. The equilibrium is thus restored, each alternate pair of leaves 

 standing in its proper normal position. The upper pair of leaves, 

 where the vegetative strength is nearly exhausted, is smaller, and re- 

 tains very nearly its normal position at right angles with the next 



lower pair. 



The specific name, amplexicaulis, is rather a misnomer if critically 

 considered. The base of the petiole is not enlarged nor clasping. 

 The thick, fleshy, succulent leaves are strictly cordate, with obtuse 

 rounded points, the petioles so short that the auricles or lobes encir- 

 cle the stem, thus giving the appearance of true amplexicaul leaves. 



"^Proceedings, p. 391. 



