PART III. | THE MECHANISMS OF FLOWERS. 551 
Rohdea juponica, Kunth.—This plant is, according to Delpino, 
a link between the Asparaginee and the Aroidew. It possesses 
a kind of spadix, on which the flowers are arranged in a close, 
uninterrupted spiral. The fact that the limb of the perianth is 
spread out exactly on a level with the points of the anthers and 
stigma led Delpino to think that fertilisation was effected by small 
animals crawling over the flowers. He observed snails (Helix 
aspersa, H. vermicularis) greedily eating the perianth, which is 
yellow and fleshy; after devouring about ten flowers they crawled 
to another spadix. Only those flowers on which the snails had 
crawled proved fertile; the flowers were found to be barren to 
their own pollen. These observations leave no doubt that snails 
are really efficient fertilising agents. 
Tritoma Uvaria is adapted for fertilisation by diurnal 
Lepidoptera (228). 
Yueca,— According to Riley (108) the species of Yucca which 
are provided with a dehiscent capsular fruit, and the moth which 
Fic. 184.—Yucca and the Yucea-moth. 
1.— Flower of Yueca recurvata, Salisb., from Georgia. Two Care of the 
perianth have been removed to show the ovary (ov) and stamens (a). § 
2.—Stigma, from above, x 44. 
3.—End of astamen, x 4}. ji, filament; po, pollen. 
4.—The Yucca-moth, Pronuba yuccasella, Riley. 
5.—Ditto, with outspread wings. se ‘ 
6.—Head. m, mandibular palp; m’, first joint of ditto; po, pollen. 
7.— Mandibular palp of female. 
8.—Ditto, of male. 
9.— Ovipositor. 
10.—A bristle from 7, 
(4—10, after Riley). 
effects their cross-fertilisation (Pronuba yuccasella, Riley) stand in 
close interdependence. In the female of this moth the first joint 
of each of the two maxillary palps is transformed into a long 
prehensile organ, which can be rolled up, and which serves to seize 
the pollen with. After the female has bored the ovary in several 
