i893. CHRISTIAN KONRAD SPRENGEL. 273 



certain flies which, deceived by the appearance, imagine the spur to 

 contain honey, and creeping in, tear the pollen masses from their 

 chambers and bring them upon the sticky stigma. Flowers of this 

 type, which have fully the appearance of honey flowers, but do not 

 contain honey, I call ' sham honey-flowers ' (Scheinsaftblumen). 

 That there are more of them, I saw in the same year on the common 

 birthwort [Aristolochia Clematitis). I found, namely, that this flower 

 also, which contains no honey, is formed in every way like a honey 

 flower, and, on this account, small flies of all kinds creep into it. In 

 the following summer I saw clearly that this flower is a true wonder 

 of nature, namely, that these flies are led by the appearance of the 

 flower to creep into it, that they may fertilise it, and that they are 

 held prisoners in it until they have done so, but that as soon as this 

 has occurred they are released from detention. 



" In the summer of the year above mentioned I discovered, in 

 Epilobium angiistifolium, something upon which I had never happened 

 before, namely, that this hermaphrodite flower is fertilised by humble 

 and hive bees, not, however, each flower by its own pollen, but the 

 older flowers by means of pollen carried b}' insects from the younger. 3 

 This observation shed great light upon many of my earlier discoveries. 

 I was especially pleased when I found a similar method of fertilisa- 

 tion in the wild love-in-a-mist {Nigella arvensis). In the summer of 

 1788 I had perceived the beautiful arrangements of the nectaries 

 of this flower. In the following summer observation showed me that 

 it was fertilised' by bees. At the time I thought I fully understood 

 how this came about. Now, however, I found that I had erred in 

 regard to the last point, because then I still believed all hermaphro- 

 dite flowers to be fertilised by their own pollen. 



" Finally, last summer I studied the common spurge {Euphorbia 

 Cyparissias) and found in it an arrangement the exact opposite of that 

 described above, the flower being fertilised by insects, but in such a 

 way that they carry the pollen of older flowers to the stigmas of 

 younger ones. 



"Upon these six chief discoveries, made in five years, is founded 

 my ' Theory of Flowers.' " 



After a discussion of the subject of nectar and its uses, in which 

 he demolishes the older views, such as that the nectar causes the 

 growth of the ovule to a seed by keeping it damp, or that it is an 

 injurious substance, whose removal by insects is therefore a direct 

 benefit to the plant, Sprengel goes on to point out how in all honey 

 flowers the following five points may be observed, viz.: — (i) The 

 honey gland or nectary ; (2) the honey receptacle, in which is stored the 

 honey secreted by the gland ; (3) some arrangement to protect the 



* The flower is dichogamous, i.e., the stamens and pistil do not ripen simul- 

 taneously. In young flowers the stamens are ripe, the style folded back out of the 

 way ; in older ones the style occupies, with its ripe stigmas, the place formerly 

 held by the now empty and withered stamens. This phenomenon is termed pro- 

 tandrous dichogamy or protandry ; the reverse case {Euphorbia) protogyny. 



