THE HIGHER DICOTYLEDONS. 341 



there are evidently two varieties of Primrose, differing only in 

 the relative lengths of stamens and style ; in the two types 

 the positions of anthers and stigma are simply reversed. In 

 which case does self-pollination seem to be possible or likely 

 to occur, and in which does it appear to be hindered ? 



Cover flowers of each kind with muslin, and find out whether self- 

 pollination does occur in either kind. With the microscope examine 

 the pollen-grains and the stigma of each kind of flower, noting that 

 the higher anthers (i.e. those of short-styled flower) produce larger 

 pollen-grains (about ^^ inch diameter) than those of the long-styled 

 flower (about y^V^ i ncn diameter) ; the long style is globular and 

 rough with small projecting hairs, while the short style is rather flat- 

 topped and smooth (with very short projections). Possibly the differ- 

 ence in size of the pollen-grains may be due to the fact that the 

 larger grains have to send a longer pollen-tube down the long style to 

 reach the ovary. Perhaps also the longer stigmatic hairs are required 

 to catch and hold the larger grains, which would tend to roll off" the 

 nearly smooth stigma of the short-styled flower. 



The fruit (capsule) of Primrose opens by five teeth (one 

 opposite each sepal) at the top, each tooth being notched in 

 the middle. This, together with the occasional production 

 of "monstrous" flowers in which the pistil is represented by 

 five Iqaves, affords evidence that the Primrose pistil is made 

 up of five carpels. 



347. In the Cowslip (Primula veris) the leaf-stalk is 

 "winged" below the blade, not forming a bare midrib at 

 the base of the blade as in Primrose. The flowers are 

 carried up on a general stalk or inflorescence-axis and are 

 arranged in an umbel, each flower having a stalk of its own. 

 The corolla is smaller than in Primrose ; the tube is shorter 

 and its " throat " is dilated below the mouth, which is more 

 funnel-shaped than in Primrose. The orange- coloured honey- 

 guides are very conspicuous, forming a patch opposite each 

 of the five lobes. The flowers are heterostyled, as in the 

 Primrose. 



348. Note on Pollination of Primrose and Cowslip. In 



both of these plants honey is produced at the bottom of the corolla- 

 tube, and the flowers are visited largely, in fine weather, by bees, 

 butterflies, and moths, whose tongues are long enough to reach the 

 honey. It has been found by experiment that, on the whole, "legi- 

 timate" cross -pollination (transference of pollen from long-styled 



