I 120 



A TEXTBOOK OF THEORETICAL BOTANY 



vascular supply to an organ may, at least in some cases, survive the organ 

 itself. This is a matter of some importance as it bears upon the much- 

 discussed question whether anatomical evidence of morphological changes 

 should be received or be ignored as too uncertain to be valuable. 



In akenes with basal ovules all three traces may be very much shortened. 

 This affects the ventral traces earlier and more strongly than the dorsal 

 trace. They may indeed in extreme cases disappear entirely, leaving the 

 ovule attached to the remaining dorsal trace, a condition which never 

 otherwise occurs. 



The persistence of vasculation above the carpels, which we have noted 

 above in the Aqidlegia type, has some bearing on the question whether a 

 carpel may be truly terminal on the receptacle, which in its turn bears on the 

 further question of whether a carpel is foliar or not, since no true leaf is 

 terminal.* 



Fig. 1096. — Diagrams showing the vasculation of receptacles bearing solitary 

 carpels. A, Primus aiitim. B, Actaea. C, Albizzia. D, Banhinia. Illustrat- 

 ing phases in the reduction of the " superfluous " vascular tissue. {After 

 Eames.) 



Most of the carpels, e.g., in Leguminosae, which used to pass as being 

 terminal, are in fact supplied by traces which are given off a short distance 

 below the end of the receptacular stele (Fig. 1096), the remaining tissues of 

 which come to an end in the base of the developed carpel (see also p. 1 1 17). 

 This is scarcely reconcilable with a truly terminal position. A similar 

 anatomical structure occurs in the base of the uppermost carpel in some 

 Ranunculaceae and Rosaceae, where there is no suggestion of terminality. 



Where there is reduction of the gynoecium to a single carpel it usually 

 appears to be terminal, but the vascular anatomy negatives the appearance. 

 The residual bundles of the axial stele which would have supplied other 



* T he latter proposition may sound very dogmatic, but it is simplv a corollary to our accepted 

 view of a leaf (see Volume I) which is that it is an appendicular structure. If therefore an organ 

 IS termmal It cannot, ipso facto, be a leaf; which is another illustration of the difficuhie? 

 encountered when we trj' to categorize the parts of the plastic living organism. 



