THE ROCK-ROSE TRIBE. 77 



the placenta, e. the ovule, and f. its foramen ; then 

 the pollen-tubes may be stated to quit the style at a., 

 to hang do\\Ti freely in the cavity of the ovary, in the 

 direction of the dotted line a. /., and thus to secure a 

 short line of communication with the foramen. 



Many more such cases are to be found by those 

 who search for them ; but none much more curious 

 than the present. 



EXPLANATION OF PLATE XXXIL 



L The Lythrum Tribe. — 1. A twig of Lythrum Salicaria, the 

 Purple Loosestrife, in flower. — 2. A flower slightly magnified. — 3. The 

 calyx cut open, showing the two rows of stamens, and the manner in 

 which they adhere to the calyx — 4. An ovary, with the style and 

 stigma. — 5- A horizontal view of the interior of the ovary, showing 

 the ovules adhering to the placentse. — 6. Half a calyx, with the ripe 

 fruit in the inside ; a one of the halves of the style, carried away on 

 the point of the valve of the fruit when it burst. — 7, A ripe seed; a 

 the raphe, with the chalaza at its end. — 8. A longitudinal section of 

 the seed, showing the dicotyledonous embryo. 



n. The Rock-Rose Tribe. — 1. A flower and leaves of the Pur- 

 ple Rock-Rose (Cistus purpureus). — 2. A calyx with the stamens and 

 ovary, a a the two outer sepals. — 3. A longitudinal section of the 

 ovary ; a the stigma, b the placenta ; this gives a good view of the 

 ovules. — 4. An anther. — 5. An ovule ; a the foramen. — 6 A ripe 

 seed-vessel, invested with the calyx. — 7. A seed vessel burst ; the seeds 

 fallen out; a a valves. — S. A seed. — 9. The same cut longitudinally, 

 showing the embryo rolled up, with the radicle at a. — 10. A diagram 

 to explain the manner in which the pollen- tubes reach the foramen of 

 the ovule. 



