48 



one species of Tliy&aiiclla and in all the species of Polygoiiclla the 

 branching is not nodal, but internodal. 



The internodal branching is brought about by the adnation of 



a secondary axis to a primary axis for a greater or less distance 



above a secondary node, usually about one-half the distance from 



node to node. The true condition is more plainly shown in Thy- 



sanella, where the union of the two axes is not as complete as in 



Polygonella, a shallow but usually distinct groove showing the 



place of union. 



Hxplanatlon of the Fijfure. 



A. Polygonella Americana (F. «& M.) Small. 



B. Thysanella fimbriata (YX\.^ h.-.Gxz.'j. 



a. Nodes. 



b. Point where the adnate axis diverges. 



