Professor Salisbury is particularly interested in the causes of distribution,
the newer causes as well as the older. We know that the railway is a distributor of seed—has, for example, carried a hire wall senecio from Oxford to Win- chester. Professor Salisbury has found out a new example of the influence of the motor-car, especially in relation to a heavy-seeded plant. nudriearia suaceolens, akin to May weed and chamomile. It has ' fruits which are mainly dispersed M mud, upon the feet of cattle, boots, tyres, &c. ; and it is very probable that the rapid extension in area of this species subsequent to 1000 was in no small measure due to the coincident increase in motor transport. The patterned tread of the motor tyre is a peculiarly efficient means of dispersal for mud containing seeds, which may be conveyed long distances before the shrinkage on drying results in its dis- lodgement from the depressions of the pattern."
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