is true if my tree strike roots essential for its life into my neighbour's soil, it must  then be held in common; but if it may continue to live without such roots it will not be  so held. For the same reason that plants cede to the soil when they strike root,  and that immovable buildings built there do, so wheat that is sown and takes root  on land cedes to it, whether it falls on the ground by accident or not.20
Things are acquired by specification.
 21Dominion is acquired by us through specification, as where one makes a new  object out of another's material; he will be the owner of the new object he made.22
 23There is another way of acquiring, [that is] by confusion. Liquids are mixed, as  honey and wine; also solids may be, as things different in kind, [for example], gold  and silver, lead and iron, though this can be done only with great difficulty. What  results from the mixture, whether the materials can be separated or not, belongs  in common to those with whose consent the bodies or species are confused. Nor  will a different result be reached if it is by accident that the confusion was made,  if the elements cannot be separated. If they can, each will have as much by weight  and measure as he had of the original materials. If one's wheat is mixed with  another's, the whole will not be owned in common by both, but each will recover  from the heap a portion equivalent to the wheat he had. Nor can there be mixture  of the wheat since the separate grains remain distinct, as [in the case where] cattle  belonging to Titius are mixed with your own, the herd is not taken to be held in  common. And though it may be very difficult and almost impossible to separate  my wheat from yours, nevertheless it may be said that a vindicatio can be given  for the undivided part, as though the heap of wheat was common, that each may  recover so much from the heap as belonged to him. Confusion differs from mixing  together in three respects: different kinds of materials are said to be mixed and  materials of the same kind confused. Different kinds of materials that have been  mixed remain the same in substance and kind; things confused are transformed  into a new object.24
 25Dominion is also acquired by finding, as where treasure is found,26 as will be  explained below [among the pleas of the crown.]27
 By the civil law dominion is acquired in many ways, namely, by the causa of  gift, succession, a testamentary causa, and many others,28
23-24. Azo, Summa Inst. 2.1, nos. 51-53; Br. has omitted Azo's third distinction: Things confused are made into a thing held in common even though confused without the consent of their owners; those mixed, only when that is done with their consent; Kantorowicz, 119-21