EVOLUTION OF PLANTS, AND THE DIRECTIVITY OF LIFE. 557 



kingdom that " disuse " brings about " degeneracy " ; so that reversions 

 to more primitive forms often occur. Thus, gardeners encourage 

 the transformation of the naturally irregular corollas of Pelargoniums, 

 Gloxinias, Pansies, &c, into regular ones. 



Again, irregular flowers are mostly situated close to the stem, so 

 that the insect must visit it from the front and not all round as in a 

 regular flower. The influence of its weight is thus " felt " only on 

 the anterior side of the flower ; but when it is a terminal flower of 

 a spike, as of Foxglove, Aconite, &c., or the middle flower of a " truss " 

 of Pelargoniums, then the flower often reacquires regularity, and 

 the honey-secreting organ is wanting, as it presumably was before 

 the ancestor became adapted to insect-visitors. Another result may 

 occur when, from migration or other cause, the flower is no longer 

 visited. It then becomes degraded in all its parts, but assumes self- 

 fertilization and is quite independent of insects. This I found to be 

 the case with all the plants I could examine in the desert near Cairo, 

 where no insects occur, or are very rarely to be seen. Self-pollination 

 is secured by bringing the anthers into direct contact with the stigma. 

 This, in fact, is their normal position in the bud-state ; but at that 

 Urn", the pollen and stigmas are not matured for pollination ; but in 

 buds which never open at all, as in Violets and many others called 

 " cleistogamous " or "concealed unions," as we might translate 

 this word, they mature simultaneously within the bud. Cold weather 

 may have the same effect. The chickweed opens its little flowers 

 in sunny weather when the filaments bear a honey-secreting gland ; 

 but in a "mild" winter it may continue to form seed while 

 permanently in bud. 



The question may be now asked : What is the " good " 

 or advantage to the plant of being crossed ? The answer depends 

 upon what we understand by the word " good." 



The two " ends " of plant-life are a vigorous existence until the 

 plant dies a natural death and the production of an abundance of 

 good seed. Now, it is notorious that self-fertilizing weeds propagate 

 to an enormous extent in a neglected garden or arable field. They 

 are usually small annuals with inconspicuous flowers ; but the result 

 is obviously in favour of self-fertilization. These and wind-fertilized 

 species of plants are by far the most widely distributed over the 

 globe. On the other hand, the plants with flowers specially adapted 

 to insects may have finer flowers, but their dispersion is much more 

 restricted. 



In experiments such as Darwin's,* when crossing is carefully 

 made, the plants receive an unnatural stimulus, and finer plants are 

 often the result, so that this process is invaluable to horticulturists ; 

 but if it be continued generation after generation with the same 

 kind of plant, the possibility of a continued improvement may com- 

 pletely fail. As examples, one well-known grower of Primroses 

 found that by repeated crossing, good seed became so difficult to 



* Cross and Self-fertilization of Plants. 



