In comparing plant and animal tumors it must bc remembered, however, that there are certain developmental and I'unctional characteristics C01- monly used in the differentiation of animal cancers that are more or less restricted to animals and cannot, therefore, be carried over and applied to plant tumors. These have been dealt with in detail by WHITE and BRAUN (1942) and by BLACK (1949), and will not be considered further here. The most essential characteristic of being able to grow independently of any morphogenetic restraint, upon which all of the other diagnostic features must ultimately...