RELATION TO ENVIRONMENT 511 



becomes still more marked in the spores of the terrestrial Arche- 

 goniates. 



Among the Fungi, which are often extremely specialized forms, 

 there are numerous instances of special adaptation of the reproduc- 

 tive parts associated with animals. In the Ergot (Claviceps pur- 

 purea), for example, the first-formed spores are accompanied by the 

 production of a sweet secretion, that is attractive to insects, which are 

 doubtless agents in the dissemination of the spores. These adhere 

 to the insects when they are seeking the honey-like secretions. 

 It is possible, also, that the sweetish substance exuded from the 

 pycnidia of some of the Rusts, etc., may serve the same purpose. 

 How far the vivid colors of many of the larger Fungi are attrac- 

 tive to insects does not seem to have been investigated, but it seems 

 very doubtful whether, in most cases, these colors have any biologi- 

 cal significance. 



Odors of Fungi. The extremely offensive odor of certain Fungi, 

 especially the Phalloideae, are, with little question, useful to the 

 plants, as carrion insects are attracted by the odor, and are almost 

 certain to carry away the spores, which in most of these are im- 

 bedded in a slimy fluid which adheres readily to the insect. 



Special mechanical devices for scattering the spores are found in 

 most of the lower plants. The violent projection of the sporangia 

 in Pilobolus and other Moulds has been referred to, and the mechan- 

 ical contrivances found in the sporangia of Mosses and Liverworts, 

 and the annulus of the Fern sporangium, have also been sufficiently 

 described. These mechanisms are usually regulated by the water 

 supply, either by the rapid absorption of water, as in Pilobolus, or 

 to hygroscopic action, as in the movements exhibited by the elaters 

 of Liverworts, or the annulus of the sporangium in the Ferns. 



Spermatophytes. It is among the spermatophytes that the most 

 perfect adaptations of the reproductive parts to their environment are 

 found. The pollen-spores are adapted to transportation by the wind 

 or by insects, or occasionally by other animals. In the former case 

 they may be provided with special buoyant organs, like the inflated 

 appendages of the pollen-spores of the Pines. Where insects are 

 the agents of transportation, the outer surface of the spores is gen- 

 erally rough, or viscid, so that they adhere readily to the insect's 

 body. 



Distribution of Seeds 



Among the Gymnosperms the distribution of the seeds is usually, 

 like that of the pollen, due to the wind. Very often, as in the Pines 

 and Firs, the seed is surrounded by a winged appendage, derived 

 from the scale upon which the seed is borne. This forms a very effi- 

 cient sail, and enables the seeds to be carried to a great distance. 



