ANGIOSPERMS. MONOCOTYLEDONS. 



433 



in Allium Cepa. If the axis of the embryo becomes the primary stem, whether it 

 grows erect or creeps in the form of a rhizome, it first assumes the form of an inverted 

 cone, which is short or elongated according 

 to the length of the internodes ; this pecu- 

 liarity, which is common to Ferns and 

 Monocotyledons, is due to the absence of 

 secondary growth in thickness ; the portions 

 of the stem first formed preserve their original 

 thickness, while each succeeding portion is 

 larger; the transverse sections of the stem 

 are thicker the nearer they are to the apex. 

 So long as this process is going on, the stem 

 is increasing in strength ; but a time comes 

 sooner or later when each portion of the 

 stem is only as thick as the preceding one, 

 and then the stem forms a cylinder, or is 

 broad and compressed, as in many rhizomes, 

 but in either case grows on with uniform 

 strength; the lateral shoots also grow in a 

 similar manner, when they spring low down 

 on the primary stem, a.s in Aloe and other 

 plants. But it not unfrequently happens 

 that the primary shoot formed by the embryo 

 soon dies away after producing lateral shoots; 

 these grow more vigorously than the parent, 

 and then hand on the further development 

 to new shoots, which produce from genera- 

 tion to generation thicker axes, larger leaves 

 and stronger roots, till at length a more 

 constant state of things supervenes and each 

 successive generation produces shoots of 

 uniform strength. If the portions of the axes of the shoots beneath the points of origin 

 of their daughter-shoots are maintained, sympodia are formed, as for example in 

 Polygonatum multiflorum ; but in many cases each shoot disappears entirely after it 

 has produced a shoot to replace it, as happens in our native tuberous Orchids, in 

 Fritillaria imperialis (Fig. 358) and Colchicum autumnale (Fig. 36O) 1 . 



The normal branching of Monocotyledons is monopodial and usually axillary ; in 

 most cases a bud is formed in the axil of every leaf, but all do not develope, so that 

 the number of branches that can be seen is often much less than that of the leaves, as 

 in Agave, Aloe, Dracaena, Palms, and many Gramineae. But sometimes several buds 

 are formed in the axil of a leaf, and beside one another where the insertion of the leaf 

 is broad, as in many bulbs ; in Musa a number of flowers stand side by side in the 



FIG. 358. Bulbs of Fritillaria imperialis in November. 

 A longitudinal section of the whole bulb reduced in size ; zz 

 the coherent lower portions of the bulb-scales, 66 their free 

 upper portions ; they enclose a cavity / which contains the 

 decayed flower-stem ; the next year's bud k is formed in the 

 axil of the innermost scale ; its first leaves wiH form the new 

 bulb, while its axis developes into the new flower-stem ; the 

 root to springs from the axis of this bud. B longitudinal 

 section of the apical region of the new bud ; s the apex of the 

 stem, b, b> b" the youngest leaves, fv and g vascular bundles. 



1 A detailed account of these very varied phenomena will be found in Irmisch, Zur Morphol. d. 

 monocotyl. Knollen u. Zwiebelgewachse, Berlin, 1850, and Biol. und Morphol. d. Orchideen, Leipzig-, 

 1853- 



[2] Ff 



