8 EXPERIMENTAL POLLINATION. 



utilized to hasten or retard flowering or to increase the total attraction of 

 a group of individuals. Changes of position are especially valuable in 

 connection with the study of normal behavior and in determining the 

 correlation between habit and intelligence in different species and indi- 

 viduals. They may deal with the cluster, the flower, or the flower part, 

 but in the last case the change is essentially a mutilation and is considered 

 as such. The simplest method is to change the entire cluster in position 

 by 90 or 180 degrees, either by bending and fastening it in the position 

 desired, or by cutting it off, placing the end in a vial or in wet cotton, and 

 attaching it alongside a normal inflorescence. The use of single flowers 

 permits a wider range of changes, as these can be turned through two circles 

 with the assumption of very different positions. Such changes not only 

 affect the appearance of the flower with respect to attraction, but they 

 necessitate a different behavior in one or more of the successive processes 

 of landing, guidance, obtaining nectar, collecting pollen, and departure. 

 A completed visit thus becomes a new problem in the solution of which 

 species and individuals exhibit striking differences. 



Concealing or disguising flowers. — This may operate upon the plant 

 or cluster, a single flower, or a part of it, such as the petals or stamen-mass. 

 When the nectary is obstructed by a cotton plug, the effect is essentially 

 one of mutilation, while the use of green leaves to mask the corolla or 

 the disguising of the rays of one species with those of another produces 

 an artificial flower in effect. Masking is primarily a device to conceal the 

 color and thus permit the determination of the role of odor, but it must 

 always be done with the effect of habit in mind. Clusters or single flowers 

 may be covered with pots, boxes, wire cages, or other objects, or they may 

 be variously disguised by means of paper, cloth, leaves, etc. The perianth 

 may be similarly covered on either one or both faces, one or more of the 

 petals covered, the anthers or nectaries masked with paper, cotton, or 

 foreign petals; in short, any part or parts may be concealed in any manner 

 that seems desirable. This is similarly true of the rays and disks of com- 

 posites, and of all vexillary organs, such as spathes, colored bracts, etc. 

 Painting the petals or other parts is also a type of masking. Finally, odor 

 may also be masked by means of glass globes, tubes, etc., permitting color 

 and form to act alone as attractive factors. 



Mutilation. — By this is understood the removal of flowers or parts, 

 the splitting or cutting of parts, and such changes of position as result in 

 a different form. The removal of flowers is chiefly significant in such 

 definite inflorescences as the umbel and head with show-flowers or ray- 

 flowers, in which all or part of either kind of flower may be cut out to dis- 

 close the role of the other. With respect to other changes a radiate head 

 resembles a single flower to a considerable degree. In regular flowers the 

 most important mutilations arise from the removal of corolla or perianth 

 in whole or in part, the shortening of the petals, or splitting them into 

 parts of various forms. The mutilation of irregular flowers may also be made 

 to throw light upon attraction, but it is particularly valuable in revealing 

 the role of the specialized parts, as in the larkspur, peas, and mints. Hoods, 

 spurs, standards, keels, and lips may be removed wholly or partly, or they 



