402 FERTILIZATION AND FORMATION OF FRUIT IN PHANEUOQAMS, 



and fruiting obviously canuot occur. It is instances of this kind that are adduced 

 by tlie older botanical writers to prove that the hermaphrodite flowers of certain 

 species are inforiile. 



Plants ha\o also been regarded as sterile from the fact that the particular 

 insects necessary for the transfer of their pollen were absent from the locality in 

 which the observations were made. Thus, Pat'th-roia Agcria, a plant not infre- 

 quently found in rocky crannies in the Southern Alps, and cultivated in large quan- 

 tity in the Innsbruck Bot.'mic Garden, was always found to be sterile in the last- 

 mentioned locality, although it flowered profusely. The flowers of the plant require 

 insects to pollinate them, as the relations of the parts are such that autogamy can- 

 not occur. Since the particular insects which visit it in its o\A'n habitat are absent 

 from the Botanic Gartlen, the plant is infertile from lack of pollination. In its own 

 home in the Southern Tyrol and Krain, where these insects are present, it ripens 

 an abundance of fruits. The same is the case with several introduced plants which 

 have become partially wild. The Sweet Flag (Acorios Calaivuf!), truly indigenous 

 to Eastern Asia, has spadices of densely-ci'owded, hermaphrodite flowers. The indi- 

 vidual fliiwers are strongly protogynous, and when the anthers open, the stigmas 

 of the same flower are already faded. Autogamy is consequently excluded. The 

 opening of the (lowers is from below upwards, and when the anthers of the lowest 

 flowers are discharging their pollen the stigmas of the uppermost flowers are still 

 capable of pollination. Could the pollen pass from the lower to the upper flowers, 

 geitonogamy would take place, but this is only possible through the agency of 

 insects, as the pollen is adhesive. In Europe, where the plant is not originally 

 indigenous, this never happens, as the insects which visit it are absent; consequently, 

 with us, Acorun is always sterile. But further east, where it is indigenous, its 

 llowei-s are pollinated by insects, and it produces its fruit in spikes of red berries, 

 The Day Lily (Hc'iiiC'rocdJlin fiiliui.) has ephemeral flowers which open in the morning 

 in summer-tinu^ between 6 and 7 o'clock, and close between 8 and 9 in the evening. 

 Its flowers are ]irotogyn(ius for a very short time. For half an hour before the 

 opening of the lluwer the mature stigma ])rojects from the tip of the perianth, 

 Simultaneously with the folding back of the perianth, the anthers liberate their 

 adhesive pollen. The style being longer than the stamens, its stigma is not auto- 

 matically pollinated. For pollination insect visits are necessary. Honey is secreted 

 at the lia,se of the tube oF i.iie ptui'inth, which is 2 cm. long. The entrance to this 

 honey is so nari-ow that only a very delicate proboscis can gain access. Beetles, 

 flies, be(!H, and other shoi't-tongued insects cannot get it, nor would they be of any 

 use for ])ollination if they eiadd. The whole ilower seems adapted for the visits of 

 Kdine larg(! butterfly with a long, thin proboscis, but curiously enough the flowers of 

 llniierdc.iilUn fiiliui, a.ro never visited by butterflies in Europe,. As autogamy is 

 excluded, the flowers remain unpollinated, and are sterile. Neither in gardens, 

 where it is much cultivated, nor in its semi-wild state does the Day Ijily ever fruit 

 with us. It is more than probable thixi Hemerocallis is visited, in Northern Asia 

 and .la]>an, whei-e it is truly indigenous, by some butterfly absent from Europe, 



