210 ON SEEDLINGS 



The most marked modification of the above type met with 

 occurs in Tunica pachygona, the seeds of which are oblong or 

 suborbicular, slightly angled at the margins, and distinctly 

 winged all round except at the micropyle, where there is 

 a narrow and moderately deep sinus, into which a little point 

 projects, containing the tip of the radicle. The wing re- 

 sults from the absence of endosperm, whereby the testa on 

 the dorsal and ventral aspect of the seed is allowed to come 

 together. Velezia also offers a rather marked modification 

 inasmuch as the seeds are deeply grooved or umbilicate on 

 the middle of the inner or ventral face, while they are ovate 

 or oblong in outline, semiglobular, thick, and convex on the 

 outer face ; the embryo is, however, straight, and the endo- 

 sperm copious. The reniform and laterally compressed type of 

 seeds may be seen by reference to Cerastium arvense (fig. 199) 

 and D. plumarius (fig. 196), showing vertical and horizontal sec- 

 tions, as well as their attachment to the central column. The 

 flattened seeds of Dianthus and Tunica are subservient to the 

 purpose of distribution by the wind, and allow of the arrange- 

 ment of a large number in a capsule, by overlapping like slates 

 on a roof. Kelatively to the size of the capsule, however, a 

 still greater number can be packed away where the seeds are 

 reniform and laterally compressed. This may be observed in 

 Saponaria officinalis, where the lateral flattening is due to 

 mutual pressure, and a large number of ovules and seeds are 

 packed away in a little space. The number is increased in cases 

 where the capsule is inflated as in Lychnis and Silene. In L. 

 vespertina the seeds are horizontal or displaced in various ways, 

 and arranged in a double series one over the other, by the 

 funicles of the two sets being of different lengths. A single ovary 

 will contain from 250 to 400, of which 240 to 370 or more 

 reach maturity. They are ridged in the direction of the longer 

 axis by the time they get ripe. Dianthus plumarius has 70 

 to 90 ovules, D. chinensis 70 to 80, and D. prolifer 35 to 45. 

 D. prolifer, it may be remarked, is an annual species with small 

 capsules. 



Most or all of the species of the tribes Alsineae and Poly- 

 carpese have small capsules with a moderate number of, some- 

 times with few, seeds. The capsule is one-seeded by arrest in 



