582 ON SEEDLINGS 



Leaves simple, entire, radical, alternate with very short inter- 

 nodes, acute, ovate- elliptic, glabrous, bright green, with petioles 

 slightly longer than the leaf, exstipulate ; midrib and two lateral 

 nerves meeting at the apex with subsidiary veins between given 

 off from the midrib. 



ALISMACE^E. 



Benth. et Hook. Gen. PL iii. 1003. 



Fruit and Seed. The ovary consists of six free carpels, or 

 more rarely three, arranged in one or many series on the 

 receptacle ; sometimes they are connate at the base and one- 

 celled. The ovules are solitary in each cell, or twin and super- 

 posed, or numerous and inserted on the interior angle ; very 

 seldom are they solitary and basal ; in the tribe Butomeae they 

 are very numerous and inserted on reticulately branched pla- 

 centas all over the walls. They vary greatly in being anatro- 

 pous, half-anatropous, amphitropous, or campylotropous with 

 an inferior micropyle. The fruit consists of free carpels, or 

 they are united at the base and dehiscent at the ventral suture 

 or indehiscent, very seldom circumscissile at the base. The 

 seeds are ovoid, oblong, or compressed, small or minute, and 

 exalbuminous with a variable testa. The embryo is condupli- 

 cately horseshoe-shaped, often thickened at the radicle, very 

 rarely straight, with the plumule hidden at the base of the 

 cotyledon. 



Seedling. Owing to the absence of endosperm in the seeds, 

 the cotyledon in this Order is probably always aerial or aquatic. 

 Alisma Plantago (fig. 684) may be given as a type. The 

 peculiarly thickened hypocotyl so frequent in the Order is 

 noticeable even from the first stages of germination. It 

 produces numerous root-hairs from the edge of the thickened 

 extremity, fixing the seedling in the soil or mud. The radicle 

 itself does not begin to elongate till five or six days after 

 germination. It is devoid of root-hairs for some time, but 

 twelve days after germination they are copious. Adventitious 

 roots commence to be given off from the first node about this 

 time. The cotyledon is subulate-linear or filiform, and sheathes 



