232 REVIEWS. 



experience would expect to obtain pure cabbage-seed, for in- 

 stance, if a plant of another variety grew within 200 or 300 

 yards." And a veteran cultivator once had his whole stock 

 of seeds seriously bastardized by some plants of purple Kale 

 which flowered in a cottager's garden half a mile away. Mr. 

 Gordon records a case of the crossing between Primroses and 

 Cowslips through pollen carried by bees over more than two 

 kilometers, or an English mile and a quarter. 



\\e must copy the close of this section — long though it 

 be — because of its capital illustration of the topic in hand, 

 and for the teleological lesson which it teaches. 



" The case of a great tree covered with innumerable her- 

 maphrodite flowers, seems at first sight strongly opposed to 

 the belief in the frequency of intercrosses between distinct 

 individuals. The flowers which grow on the opposite sides 

 of such a tree will have been exposed to somewhat different 

 conditions, and a cross between them may perhaps be in some 

 degree beneficial ; but it is not probable that it would be 

 nearly so beneficial as a cross between flowers on distinct 

 trees, as we may infer from the inefficiency of the pollen 

 taken from plants which have been propagated from the same 

 stock though growing on different roots. The number of bees 

 which frequent certain kinds of trees when in full flower is 

 very great, and they may be seen flying from tree to tree more 

 frequently than might have been expected. Nevertheless, if 

 we consider how numerous are the flowers, for instance, on 

 a Horse-Chestnut or Lime-tree, an incomparably larger num- 

 ber of flowers must be fertilized by pollen brought from other 

 flowers on the same tree, than from flowers on a distinct 

 tree. But we should bear in mind that with the Horse-Chest- 

 nut, for instance, only one or two of the several flowers on the 

 same peduncle produce a seed ; and that this seed is the pro- 

 duct of only one out of the several ovules within the same 

 ovarium. Now we know from the experiments of Herbert and 

 others that if one flower is fertilized with pollen which is 

 more efficient than that applied to the other flowers on the 

 same peduncle, the latter often drop off ; and it is probable 

 that this would occur with many of the self-fertilized flowers 



