270 Transactions. — Botany. 



At this stage the root and hypocotyl are together 11-5 mm. in 

 length, and the root is T5 mm. in diameter. Next the hypo- 

 cotyl grows upwards, and by the time it has risen arching out 

 of the soil to a height of 5 mm. the green base of the coty- 

 ledons is appearing above the ground. The part of the hypo- 

 cotyl which is arched downwards rapidly becomes straight, 

 and the cotyledons enclosed entirely or partly by the seed- 

 coat, and often by the remains of the carpel also, are raised 

 with their laminae closely pressed together and horizontal. 

 The cotyledons grow rapidly in length and width, only the tip 

 remaining enclosed in the seed-coat, which finally is cast off. 

 Then the cotyledons open out, becoming horizontal or having 

 their apices pointing downwards and their bases almost 

 touching or sometimes even overlapping. As development 

 proceeds the petioles lengthen considerably, until they finally 

 become half the length of the larninas, rhe bases of which are 

 now 6 mm. or more apart. By this time the plants are 

 twenty-four days old, and have roots 5 - 5cm. in length, with 

 cotyledons (lamina) 11mm. x 10 mm., petioles 5 - 6 mm., and 

 the 1st leaf is 8 mm. in length, with its lamina equalling the 

 petiole and just unfolding. 



Root of great length, deeply descending; lateral rootlets 

 not numerous. 



Hypocotyl at first tender, succulent, green and occasionally 

 marked with pink, soon becoming stout and woody, terete, 

 glabrous except for a few short hairs above, smooth, finally 

 16 mm. long and much thickened at the base. 



Cotyledons (when fully grown) variable in size and shape, 

 sometimes not of equal size on same plant ; lamina 9 mm. x 

 9 mm. or thereabouts, rotund or obovate-rotund, often cuneate 

 at the base; sometimes quite entire, but usually lobed or irregu- 

 larly crenate on upper third of margin, pale-green, glabrous; 

 nerves five ; venation much reticulating ; apex rounded ; peti- 

 oles spreading, 5 mm. in length, channelled on upper surface. 



Before the cotyledons have emerged from the seed-coat 

 they have their upper surfaces pressed closely together ; the 

 apical portions are folded together upon themselves, and bent 

 so as to be closely enclosed by the conduplicately folded lower 

 three-quarters of the lamina. This remains of the folding of 

 the apical portion of the lamina may be seen in the fully ex- 

 panded cotyledons, where towards the apex of the one is a 

 slight depression, and towards the apex of the other a still 

 more slight protuberance. Lord Avebury explains that this 

 folding of the cotyledons in certain of the Maivacecz causes 

 the obscure lobes on the cotyledons." 



* " A Contribution to our Knowledge of Seedlings," London, 1892, 

 vol. i., pp. 40, 41, and 245, fig*. 79, 80, 81, and 35. 



