Birds as Destroyers and Distributers of Weed Seeds. 77 



thrush fed with Bib es petraeum at 8 a.m. 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 ; but the majority of seeds took from one and a 

 half to three hours to perform the journey. Curiously enough, the 

 small smooth fruits of Myosotis sylvatica and Panicum diffusum 

 were retained for the longest period. 



Kerner goes on to observe that of the fruit and seeds which 

 passed through the intestine, 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. In the case of a few berries, 

 however, e.g., Berberis, Ribes, L&mcera, the period of germination 

 was hastened by this ingestion; while the seeds of such plants as 

 grow on richly-manured soil, e.g., Amarantkus, Polygonum, Urtica, 

 after passing uninjured through the intestines, produced stronger 

 seedlings than did those which were cultivated without such pre- 

 liminaries. 



"From these experiments we may assume 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 fleshly fruits are undoubtedly 

 disseminated in this 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. 



"Seeing that the seeds and stones containing seeds of the 

 fleshly fruits eaten by thrushes and blackbirds only remain a 

 short time in the crop and intestine of the bird, it is probable 

 that the plants in question are disseminated by this agency to the 

 distance of a few leagues at most, in the course of a single year, 

 and that it takes many years to distribute them, step by step, as 

 it were, over large areas. We may reasonably suppose that dis- 

 tribution is affected principally in the direction of those parts of the 

 world towards which thrushes and blackbirds are in the habit of 

 journeying by short daily stages when autumn, the season of the 

 maturity of most fleshly fruita, sets in. 



"It is well known that nutcrackers, jays, squirrels, and 

 marmots, keep stores of food in larders, which they fit up in holes 



