﻿66 MacDougal: A Contribution to 



veloped by this arrangement. If a tendril fails to grasp a support 

 it soon dies and is cast away in the same manner as useless leaves 

 or pinnae. 



Concerning the history of the development of tendrils on seed- 

 lings, Schenk says " Von Eutada scandcns habe ich eine Keim- 

 flanze im Bonner Bot. Garten beobachtet Aus dem dicken 

 grossen Samen kommt ein langer diinner Hauptstengel hervor, 

 dessen erste Blatter keine Spreiten entwickeln, sondern am Ende 

 des Stieles nur je eine Doppelranke tragen. Erst wenn der Stengel 

 einige Fuss hoch ist, folgen auf diese rankenartigen Niederblatter 

 normale gefiederte Blatter mit endstandiger Doppelranke."* 



Seedlings grown in a plant house at the University of Minne- 

 sota exhibit four or five basal club-shaped bracts attaining a length 

 of 8 or 9 mm. before dropping away. The fifth leaf consisted of a 

 short midrib bearing a pair of irregular stubby pinnae 2 mm. in 

 length, near the base, and a pair of tendrils springing from a point 

 I mm. from the tip of the midrib. The basal pinnae bore lateral 

 papillose extensions 8 mm. in length representing pinnules. The 

 tendrils attained a length of 7 mm. and assumed Hie normal nosi- 



tion but were not at any time capable of reaction or of grasping 

 an object. The entire petiole and midrib measured 17 mm. and 

 reached its maturity at a time when the plant stood 19 cm. above 

 the ground. The sixth leaf was furnished with two pairs of lateral 

 branches beside the apical pair of tendrils. In other plants the 

 i mperfect tendrils or the branching of the rudimentary rachis did 

 not occur until the sixth leaf had appeared. The leaves succes- 

 sively increased in size and were functionally perfect both as to 

 tendrils and laminae at a varying distance from the base. 



Anatomy. 



The tendrils are tapering cylindrical, 5-6 cm. in length, when 



first exposed they adhere by the adjoining surfaces in such manner 



£ to present a D-shaped outline, and do not separate and become 



irritable until a length of 1.5 or 2 cm. is attained. In the mature 



tendril the arrangement of tissue is strictly isodiametric. A radius 



^mr— nniiii inn i«i*riii^Miii n - ^^m^t\ 



Beitrigi 



1892. 



