MONOCOTVLEDONS. r.^ 



sheath-like structure, the first leaf or cotyledon, which developes either into a 

 sheath-like cataphyllary leaf or at once into the first green foliage-leaf of the 

 young plant (as in Allium). Within the cotyledon there is generally a second 

 and sometimes (in Grasses) a third and fourth leaf, which protrude on germination 

 out of the sheath of the cotyledon, increasing by intercalary growth at their base ; 

 these and the leaves which are formed subsequently are larger the later they are 

 formed on the growing axis. The axis usually remains very short during germi- 

 nation without forming any distmct internodes (Allium, Palms, &c.), or it lengthens 

 more rapidly and becomes segmented into evident internodes (Zea and other 

 Grasses). 



The increase in strength of the plant may take place by the powerful growth 

 of the axis of the embryo itself, so that this at length forms the primary stem 

 of the mature plant bearing the organs of reproduction, as for instance in most 

 Palms, Aloes, Zea, &c. If the axis of the embryo remains short while it increases 

 in strength, it may grow considerably in thickness and form a tuber (Fig. 389), 

 or, if the bases of the leaves become thick (as in Allium Cepa), a bulb. If the 

 axis of the embryo itself developes into the primary stem, whether into an upright 

 one or a creeping rhizome, it first of all takes the form of an inverted cone, 

 which is elongated or abbreviated according to the length of the internodes. 

 lliis peculiarity, which belongs to Monocotyledons in common with Ferns, depends 

 on the absence of any subsequent increase in thickness ; the portions of the stem 

 first formed retain their size, while each successive portion is larger ; the diameter 

 of the stem is therefore so much larger the nearer it is taken to the apex. As 

 long as this growth proceeds, the stem continues to grow stronger; but sooner 

 or later there comes a time when ever}^ portion of the stem acquires the same 

 thickness as the previous one ; the stem then becomes cylindrical, or, if it is 

 compressed like some rhizomes, still with a uniform breadth. The lateral shoots 

 exhibit the same peculiarity when they spring low down from the primary stem 

 (as in Aloe, &c.). But the primary shoot which springs from the embryo not 

 unfrequently disappears after producing lateral shoots which grow more vigorously 

 than it and then again transfer the further grow^th to new shoots, which now 

 produce from generation to generation thicker axes, larger leaves, and stouter 

 roots, until at length a condition again results in which each successive generation 

 of shoots produces others of equal strength. If the portions of the axes of the 

 shoots beneath the points where the shoots of the next order arise are persistent, 

 synjpodia arise (as represented in Fig. 135, p. 165); but frequently each shoot 

 entirely disappears after producing one of the next order, as for instance in 

 our native tuberous Orchids (Fig. 150, p. 198), or in the crown-imperial (Fig. 390) 

 or autumnal crocus (Fig. 391 )^ 



The normal Mode of Branching of Monocotyledons is always monopodia! 

 and usually axillary 2; a bud is generally formed in the axil of each leaf, but often 



^ Further details of the great vaiiety of modifications of these processes of growth will be found 

 in Irmisch, Knollen und ZwiebelgewSchse (Berlhi 1850), and Eiologie und Morphologie der 

 Orchidcen (Leipzig 18^3^. 



- According to Magnus (Bot. Zeit. i' 69, p. 770) the flower of Naias occupies exactly the place of 



