io8 A HISTORY OF BIRDS 



berries of Phytolacca. One species of this genus, P. decandra, 

 a native of North America, is used as a source of colouring 

 matter in the making of wine, and for other purposes. When 

 fleshy fruits with seeds of a diameter exceeding 5 mm., such 

 as those of Berberis, Ligustrum, Opuntia and Viburnum, were 

 introduced into the crop, the pulp passed into the gizzard, but 

 all the seeds were thrown up. And the seeds of fleshy fruits 

 which were greedily devoured were thrown up if the stones 

 which they enclosed measured as much as 3 mm. In some 

 cases seeds, as those of Lychnis flos-Jovis, were carefully re- 

 moved from the rest of the food with which they had been 

 mixed. 



The interval of time between ingestion and evacuation in 

 the birds of this third group (Thrushes) was very short. A 

 Thrush fed with Ribes petraum at 8 A.M. excreted numbers of 

 seeds after the lapse of three-quarters of an hour, and seeds of 

 Sambucus nigra passed through the alimentary canal in half an 

 hour ; but the majority of seeds took from one and a half to 

 three hours to perform this journey; though, curiously enough, 

 the small seeds of Myosotis sylvatica and Panicum diffusum 

 were retained for the longer period. 



Of the fruits and seeds which passed through the intestine 

 of one or other of these birds 75 per cent, germinated in the 

 case of the Blackbird, 85 per cent, in the Thrush, 88 per cent, 

 from the Rock-thrush, and 80 per cent, with the Robin. But 

 the germinating power of these seeds seems, as a rule, to suffer 

 a check — in from 74 to 79 per cent, of the cases examined by 

 Kerner — though the ultimate vitality of the seed does not appear 

 to suffer in any way. This point was established by, control 

 experiments, the seeds of similar fruits, and we presume from 

 the same plant, which were sown directly germinating quicker 

 than those which had been swallowed. In a few cases, how- 

 ever, as in the case of a few berries, e.g., Ribes, Berberis, Loni- 

 cera, germination was hastened by this ingestion ; while the 

 seeds of such plants as grow on richly manured soil, e.g., Am- 

 aranthus, Polygonum, Urtica, after passing through the in- 

 testines of birds actually produced stronger seedlings than did 

 those which were cultivated without having passed this test. 



Thus then we may assume that the brightly coloured fruits 

 which distinguish so many plants have been evolved by the 



