578 



ON SEEDLINGS 



not always, aerial, and carries the seed up with it during 

 germination. The testa is ultimately dropped, generally 

 by the decay of the tip of the cotyledon. The hypocotyl 

 of Bowiea volubilis (fig. 682) is undeveloped ; 

 and the primary root soon superseded by fleshy, 

 adventitious roots. The cotyledon is terete and 

 solid except at the base, which is hollow and 

 sheaths the plumule ; it becomes very much in- 

 flated there, constituting the first tunic of the 

 bulb. It varies greatly in length, from 10-23 cm. 

 in different seedlings. The first leaf resembles 

 the cotyledon except in being very much shorter. 

 The leaves of the adult plant arise from the bulb 

 and are deciduous ; those of the much branched 

 and twining flower stem are reduced to bracts. 

 On small bulbs the radical leaf is solitary, semi- 

 terete, and channelled on the upper surface. 



The primary root of a species of Tulipa (fig. 

 683) from Afghanistan is short, fleshy, un- 

 branched, and soon dies away. The hypocotyl 

 is undeveloped, and the cotyledon is terete, 

 thickest in the middle, tapering each way, and 

 carries the testa for a time at its apex. It soon 

 becomes gibbous at the base, and then develops 

 into a blunt tube which penetrates the soil, 

 carrying the plumule down with it at the bottom 

 of the tube, and both together constitute the 

 first bulb. The object of this peculiar growth is 

 to bury the bulb at a sufficient depth in the soil. 

 The process is repeated in succeeding years when 

 fresh growth is being made, in order to carry it 

 still further beneath the soil as it gains strength. 

 No true leaves are developed during the first 

 ~Bowiea year of the plant from seed. 



volubilis. 

 Half nat. size, Bowiea volubilig> jg-^ (fig _ QQ ^ 



Primary root tapering downwards, transversely wrinkled 

 flexuose, with flexuose lateral rootlets, soon superseded by long 

 fleshy, colourless and, at least in the early stages, unbranched 

 adventitious roots. 



