THE COURSE OF THE POLLEN-TUBE. 



411 



the ovary, sometimes towards the central column, as in the Star of Bethlehem 

 (Ornithogalum, figs. 31 5 3 > 4 - 5 ); whilst frequently the ovule is inverted so that the 

 micropyle faces the base of the ovary (cf. fig. 211 8 , p. 79). Since, in the majority 

 of plants, several ovules are contained in a single ovary and each is fertilized by a 

 separate pollen-tube, we find a number of tubes traversing the style, and, on their 

 entering the cavity of the ovary, diverging to the several ovules. One would 

 expect now to find this portion of the route to be followed by the pollen-tubes well 





Fig 814 -The course of the pollen-tubes to a Kock-rose (HetonflWmum marifoKum). 

 single flower,natural., Z ,*Aflower,strippedo, r ^^^^^ 



section ; the pollen-tubes are seen passing down the stj o ine 3 ^ devious course, first down the inside 



indicated erroneously as going direct to the micropyles ; actually i n y ^ ^ ^ ^ longitudinal section ; shows 



wall of the ovary and then up to the^ micropyles); x 22 L B "B ti 65> 4 A dry pollen-grain; x 300. A 



,. ^-**.-M ^^f5/, r> Q ni11 and tube {g ^, ,*, nnnoiml form, the 



indicated, either mechanically a, by furrows and grooves, or by lines of secrecy 

 and nutrient cellsleading to the micropyl. This, however, "*?* 



u- - 



