AND CROSS-BREEDING. 147 



that are so familiar in the spring, and may be found in abund- 

 ance about July and August, very small, but still not difficult 

 to make out. On opening them there is no trace of petals ; 

 there are five stamens, with long filaments and very small 

 anthers, offering scarcely any resemblance to those of the 

 open flowers, which have very large anthers and no filaments. 

 The pollen, again, very small in quantity, is contained in two 

 almost transparent bags at the base of the anther, and is dis- 

 charged directly on to the stigma. The pistil consists of a 

 conical ovary, and a very large stigma curved completely over 

 in a semicircle so as to bring the papillose receptive surface 

 into a horizontal position in which it will most readily receive 

 the pollen. A most instructive contrast is afforded between 

 the arrangements of the reproductive organs in these two 

 kinds of flowers on the same plant. In the showy spring 

 flowers the stigma projects horizontally in the form of a beak 

 above and quite clear of the stamens, the arrangement of 

 which is such that it is scarcely possible for any of the pollen 

 to reach the stigma without the intervention of insect agency. 

 In the closed summer flowers it will be seen that the arrange- 

 ments have evidently an exactly opposite purpose. They 

 produce abundance of seed. Another section of the genus 

 Viola, of which the wild Pansy ( Viola tricolor] may be taken 

 as a type, produces no cleistogamous flowers ; and the con- 

 trivances for the fertilisation are, as has already been men- 

 tioned, quite different from those in the true Violet 



In two Indian species of Campanula, the closed flowers are 

 described by Professor Oliver as being altogether different in 

 shape to the conspicuous ones. They are covered by a com- 

 pletely-closed membrane, the rudiment of the corolla ; the 

 stamens are extended horizontally, and the anthers are quite 

 connate, and together adnate to the stigma. As the flowers 

 have only at present been observed in dried herbarium speci- 

 mens, the mode in which the pollen-grains reach the stigma 

 is still uncertain. In Juncus bufonius it is said that the 

 pollen-tubes are emitted while still within the anther, the 

 wall of which they pierce. In the Wood-sorrel, Oxalis aceto- 

 sella, the closed flowers, which appear towards the end of the 

 summer, resemble much more closely the well-known spring 

 flowers, which are in this case certainly fertile. In accordance 

 with the ordinary practice of economy by nature, the amount 

 of pollen in the cleistogamous is generally very much less than 

 in the open flowers, since it has very little chance of being 

 wasted. In the small flowers of Malpighiacese, Jussieu states 

 that there are only a very few grains 'of pollen; in those ot 



