THE LILY FAMILY. 375 



eye or bud to each portion, and a large proportion of these 

 buds develop themselves if planted in boxes or pans of moist 

 earth, and subjected to a genial bottom-heat. They may also 

 be propagated by ringing the stems below the crown of sword- 

 shaped leaves, and covering the cut part with a pot filled with 

 moist earth, into which roots will be emitted, after which sever 

 the stem entirely, and plant at once where it is to remain. 

 A box of earth is often more convenient than a pot in opera- 

 tions of this kind. If the roots of many of the strong-growing 

 hardy Yuccas are examined, they will be found to produce 

 tubers or " knaws," and these often develop roots and shoots 

 if removed and planted in pans or boxes on a genial bottom- 

 heat. They are simply fleshy root-buds, and they succeed 

 best if they are only partly buried in the soil. Y. aloifolia and 

 its beautiful variegated forms may be propagated either by 

 stem-cuttings (eyes) or cuttings of the thick fleshy portions of 

 the root. I am not aware that any attempt has been made to 

 fertilise or hybridise these plants in our gardens ; and if this is 

 attempted, it must be remembered that their flowers open at 

 night. It appears possible that on their native plains these 

 plants are fertilised by nocturnal lepidoptera or other insects, 

 and this may account for their not often bearing perfect seeds 

 in cultivation. Plants artificially fertilised would doubtless 

 furnish plenty of seed ; and now that their stately beauty is 

 beginning to be admired, they will be much sought after, and 

 increase in value. 



Since the above was written, I find that Prof. Riley of St 

 Louis, the state entomologist of N. America, has discovered 

 that Yuccas are fertilised by a small white moth, which he calls 

 Pronuba yuccasella, an insect which forms the type of a new 

 genus. The female insect only has maxillary palpi, wonder- 

 fully modified into a long prehensile tentacle, with which she 

 collects the pollen and thrusts it into the stigmatic tube ; and 

 after having thus fertilised the flowers, she consigns a few eggs 

 to the young fruit, the seeds of which afford the food necessary 

 for the existence of the newly-hatched larva. The Yucca is 

 the only entomophilous (insect-loving) plant known which 

 absolutely depends for fertilisation on a solitary species of 

 insect,* and it is curious to note how admirably that insect is 

 modified in its structure, as if especially for this purpose. It 

 is curious also to observe that the pollen of Yuccas is glutin- 

 ous, and is expelled from the apex of the anthers before the 



* The same thing is suspected by Darwin to be the case with one of the 

 most singular and the largest- flowered of all Orchids, Angracum sesqui- 

 pedale of Madagascar (see Darwin, " Fertilisation of Orchids "). 



