56 ON SEEDLINGS 



auricles seem to be of little use to the young plant. For 

 instance, the embryo of Cuphea, while in the seed (fig. 84) 

 has very large auricles, which in the seedling (fig. 103, A-C) 

 soon disappear. In Ruellia, again (fig. 55), we have a similar 

 case. 



SIZE OF SEEDS. 



As regards the size of seeds, if we could imagine a state of 

 things in which every seed grew and attained maturity, then 

 to keep up the number of any given species existing at any 

 time, it would be sufficient if each plant produced but one or 

 two seeds during its whole life. There is, however, an 

 enormous destruction of seeds. The great majority are eaten 

 by animals, or fail to secure a suitable site for germination ; 

 of those which do germinate, again, many are crowded out by 

 their fellows. Darwin observed that out of 357 seedlings 

 which came up in a space of 3 feet by 2, no less than 295 were 

 destroyed by slugs and insects. Now the greater the chance 

 against any given seed reaching a suitable locality and attain- 

 ing maturity, the larger number of seeds must the plant pro- 

 duce in order to maintain its numbers, and, as a general rule, 

 the smaller will the individual seeds be. On the contrary, 

 the greater the chance that each seed enjoys of arriving at 

 maturity, the smaller the number of seeds that is necessary, 

 and in such cases it is an advantage that the seeds should be 

 large. 



Hence parasitic plants generally produce a large number 

 of very small seeds, though there are exceptions due to other 

 considerations, as, for instance, in the Mistletoe (I believe, 

 indeed, in all the Loranthacese), where the seeds are carried 

 by birds. 



An interesting illustration is afforded by certain species 

 which produce two kinds of pods, as, for instance, Cardamine 

 chenopodifolia of Brazil. Besides ordinary pods, which re- 

 semble those of any other Cardamine, and contain several 

 seeds, this plant produces a second sort of pod underground. 

 Now in the ordinary pods the number of seeds increases, of 

 course, the chance that some one will find a suitable place. 

 On the other hand, the subterranean pods are sown, as it were, 



