214 ON SEEDLINGS 



show an alternate, penninerved venation. While yet in the 

 seed they are linear, longer than the radicle, incumbent, and 

 otherwise resemble those usually found in the reniform or 

 suborbicular and laterally flattened type of seeds, but after 

 germination they become successively oblong-elliptic, elliptic, 

 and ultimately suborbicular, so that their form is due to growth 

 subsequent to germination, and does not depend upon that 

 which obtains while yet in the seed. 



A third type is shown by Saponaria Vaccaria. The coty- 

 ledons are narrowly oblong, obtuse, shortly petiolate and 

 penninerved, and closely resemble the primary leaves in that 

 respect as well as in form. The seed is large (3-4 mm. in 

 width), suborbicular, and slightly flattened laterally. The 

 embryo is also large and curved round the periphery, and the 

 cotj'ledons in germination keep much the same shape but 

 attain a large size on account of the large store of reserve 

 material in the seed. They are also unequal in size hi the 

 proportion of 25 to 29 mm. ; and this peculiarity no doubt 

 takes its origin in the seed, where the outer cotyledon would 

 be the longest. They are long and narrow during germination, 

 but increase in width afterwards. Lychnis Githago has 

 long and broadly spathulate, sessile cotyledons connate at 

 the base. They are opaque and show a midrib only. 



A large number of species have broad cotyledons of 

 moderate length somewhat similar to those of Dianthus, but 

 they are pointed and more or less evidently narrowed at both 

 ends. Those that may be grouped under this head vary some- 

 what between ovate-lanceolate, ovate, and elliptic or oblanceo- 

 late; but all agree in being pointed. Cerastium arvense 

 (fig. 200), Silene echinata, and Silene rubella may be given as 

 representatives of the three subtypes respectively. The coty- 

 ledons of C. arvense are ovate-lanceolate, petiolate, obtusely 

 pointed, slightly mucronate, tapered to the base, distinctly 

 one-nerved, and connate at the very base. Those of Silene 

 echinata are broadly ovate, short, moderate in size, shortly 

 petiolate, and faintly trinerved. Those of S. rubella are 

 oblanceolate, tapered to a rather broad, connate base, and 

 unequal in size in the ratio of 9'5 to 11 mm, Silene 



