864 THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. 



blackbird was tbe least fastidious about its food. It even swallowed the fruits of 

 the Yew without afterwards relieving its crop of the stony seeds, and it never 

 rejected a single fruit that was mixed with its food. The song-thrush refused all 

 dry fruits of 5 mm. diamater or more, even when they were mixed with the finely- 

 chopped meat with which the bird was fed. They also avoided certain strong- 

 smelling fruits, such as that of the Yarrow. On the other hand, the aromatic fruits 

 of Umbellifez'ae (e.g. Bupleurum rotundifolium and CaruTn Carvi) were eaten with 

 great avidity. The seeds of the Tobacco-plant, Henbane, and Foxglove mixed with 

 the food were not rejected and caused no ill eflects, and no more did the berries of 

 the Deadly Nightshade, which were devoured greedily. On the other hand, a song- 

 thrush sickened after eating berries of Phytolacca. When fleshy fruits with seeds 

 of diameter exceeding 5 mm., such as those of Berberis, Ligiistrwm, Opuntia, and 

 Viburnum, were introduced into the crop, the pulp passed thence into the gizzard, 

 but all the seeds were thrown up. Many seeds, as, for example, those of Lychnis 

 flos-Jovis, were carefully removed from the rest of the food with which they had 

 been mixed. The seeds of fleshy fruits which were greedily devoured were thrown 

 out of the crop if the stones which they inclosed measured as much as 3 mm. The 

 interval of time between ingestion and evacuation was surprisingly short in the 

 birds of the third group. A thrush fed with Ribes petrceum at 8 o'clock in the 

 morning excreted numbers of the seeds after the lapse of three quarters of an hour, 

 and seeds of Sambucus nigra were found to have passed through the alimentary 

 canal in half an hour. The majoi'ity of seeds took from li to 3 hours to perform 

 the journey. Curiously enough, the small smooth fruits of Myosotis sylvatica and 

 Panicurn, diffusum were retained for the longest 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 case of the thrush, 88 

 per cent in the case of the rock -thrush, and 80 per cent in the case of the robin. 

 The germination of fruits and seeds that had undergone ingestion and excretion was 

 usually (i.e. in from 74 to 79 per cent of the cases) tardy as compared with that of 

 similar fruits and seeds which had not been treated in this way but were only germi- 

 nated for the purpose of comparison. Only in the case of a few berries (e.g. Berberis, 

 Ribes, Lonicera) was the period of germination hastened. The seeds of such plants 

 as grow on richly-manured soil (e.g. Atnaranthus, Polygonum, Urtica) after passing 

 uninjured thi-ough a bird's intestine produced stronger seedlings than did those 

 which were cultivated without such preliminaries. 



From these experiments it is evident that the dispersion of edible fruits through 

 the agency of thrushes and blackbirds is not, as was formerly supposed, an 

 exceptional phenomenon obtaining in the Mistletoe only, but one that may take 

 place in the case of many other plants, and other observations prove that, as a 

 matter of fact, it does take place. Plants possessing fleshy fruits are undoubtedly 

 often disseminated in tliis manner. The occurrence of such plants as epiphytes upon 

 trees, and also their unexpected appearance on the tops of high rocks and old walls 

 thus receives a natural explanation. 



