XV] ULODENDRON 131 



It is obvious that in these cups we have the scars of some 

 lateral organ, but the evidence afforded by specimens of which 

 the depressions contain the remains of such organs is by no 

 means conclusive. A Ulodendron has been figured by D'Arcy 

 Thompson', in which the lower part of a lateral organ is 

 attached by a narrow base to one of the scars, but the pre- 

 servation is not sufficiently good to enable us to decide whether 

 the organ is a cone or a vegetative shoot. Kidston^ has 

 described other examples showing portions of organs in con- 

 nexion with the scars, but an examination of the specimens in 

 his collection failed to convince me that his interpretation of 

 them as strobili is correct. 



The phenomenon known as cladoptosis, as shown on a stem 

 of the Conifer Agathis^ and certain Dicotyledonous trees such 

 as Castilloa, suggests a possible explanation of the Ulodendron 

 scars. This comparison was made by Shattock* in 1888, but he 

 did not accept the resemblance as a real one. An objection 

 may be urged to the cladoptosis hypothesis that in Ulodendron 

 the branch, whether vegetative or reproductive, was not 

 attached to the whole of the depressed area. On the other 

 hand, a lateral branch originally attached by a narrow base 

 may have continued to increase in diameter until its base 

 became slightly sunk in the bark of the stem, thus producing a 

 cup-like depression which, on the fall of the branch, would 

 retain traces of the original surface-features of the stem. 



Mr Watson = of Manchester recently published a paper on 

 Ulodendron scars, in which he adduces fresh and, as it seems 

 to me, satisfactory arguments in favour of the branch- 

 scar hypothesis. Fig. 158, from one of Mr Watson's blocks, 

 illustrates the nature of his evidence. He points out that in 

 the obverse half of a large specimen of Bothrodendron in the 

 Manchester Museum, the umbilicus consists of a cylindrical 

 hole, 18 mm. deep and 8 mm. in diameter, surrounded by a 

 projecting ring of mineral material which doubtless represents 

 some portion of the original plant : on the reverse half of the 



1 Thompson, D'Arcy (80). ^ Kidston (85). 



3 Seward and Ford (06) PI. xxiii. fig. C. " Shattock (88). 



« Watson (08). 



