160 PRINCIPLES AND CONCLUSIONS. 



as serious (1902 3 :657). In order to remove the petals before the flowers 

 were visited by insects, Giltay excised them before the corolla expanded, 

 which led to the flowers being handled for too long a time. He also paid no 

 attention to the behavior of the insects on the mutilated and on the intact 

 flowers. Hence, Plateau took precautions to work on Papaver orientate, 

 a species more abundantly visited and easier to observe than P. rhoeas, 

 to remove the petals with the minimum of disturbance, and to observe the 

 number and behavior of the insects in minute detail. In addition some 

 buds were enclosed in netting and the stems tied to stakes to prevent the 

 access of insects and the transfer of pollen in consequence of being shaken 

 by the wind. During a typical period there were 1 fresh and 18 old de- 

 corollate and 13 normal flowers under observation. The single fresh muti- 

 lated flower received 20 visits, of which 17 were made by Apis and 3 by Halic- 

 tus. During this time the 13 normal flowers yielded 56 visits, or an average 

 of 4.3 to 20 for the mutilated one. While frequent visits were made to old 

 decorollate flowers, these were always brief, the insect quickly recognizing 

 its error. The total number of visits to 30 multilated flowers was 137, Apis 

 making 97 and Halictus 19, while 70 normal flowers received 172 visits, 

 of which Apis contributed 121 and Halictus 18. The former received an 

 average of 4.5, the latter of 2.4 visits. As to the weight of seed, the 70 

 capsules of the intact flowers produced 21.07 gm., and those of the mutilated 

 ones 6.5 gm.; the respective averages per capsule were 0.30 and 0.21 gm., 

 giving a ratio of 1:1.39 in favor of the normal flowers. In the matter of 

 germination no difference was found between the two kinds of flowers. 



In conclusion, the removal of the petals reduced the number of seeds 

 per flower, as Giltay had shown. This result probably did not come from 

 the removal of the attractive corolla, since the mutilated flowers received 

 as many or even more visits than the normal ones. It was really due to the 

 different behavior of the insects on the two flowers in their quest for pollen. 

 They hang from the stamens of the decorollate flowers and pull them below 

 the ovary, with the consequence that they neither carry pollen to the stigmas 

 nor shake any upon it. On the contrary, in the normal flower they pass 

 between the corolla and the crown of stamens, which they shake vigorously 

 by the movements ; they also wander over the stigmatic disk. As a conse- 

 quence, the mutilated flower is reduced to the less effective autogamy, while 

 the normal benefits by the action of allogamy. 



New experiments with artificial flowers. — In reply to a number of his 

 critics, Plateau performed a much more comprehensive series of tests with 

 artificial flowers in 1904 and 1905, in the course of which he made 66 experi- 

 ments of an hour's duration with 10 different genera, 5 of which were 

 composites (1906 2 :3). His criticisms of the methods of Andreae, Reeker, 

 Wery, and others are considered later under the authors concerned, and the 

 present account is restricted to his own investigations and the consequent 

 conclusions. In making the artificial flowers especial pains were taken to 

 avoid the use of any attractive material whatsoever, as well as to copy the 

 flower faithfully as to habit, size, and color. Translucid colored papers of 

 the usual kind were employed alone for the flowers of thinner texture, while 

 for others the paper was first pasted upon tarlatan cloth, but without alter- 



