. The classification of flowering plants. Plants. V] ORCHIDACEAE 347. slit below its tip, which, opening more and more, forms a pale- green leaf-like structure with involute edges, and composed only of parenchymatous tissue. From the cleft of the first leaf the second soon emerges opposite and similar to the first, but arising a little higher up on the crown of the tu- bercle. One or more suc- cessively larger and more developed leaves form a transition to the hrst foliage-leaf, or the leaf succeeding the primary one may bear a narrow blade (fig. 163, E). The first adventitious root also break
. The classification of flowering plants. Plants. V] ORCHIDACEAE 347. slit below its tip, which, opening more and more, forms a pale- green leaf-like structure with involute edges, and composed only of parenchymatous tissue. From the cleft of the first leaf the second soon emerges opposite and similar to the first, but arising a little higher up on the crown of the tu- bercle. One or more suc- cessively larger and more developed leaves form a transition to the hrst foliage-leaf, or the leaf succeeding the primary one may bear a narrow blade (fig. 163, E). The first adventitious root also breaks through near the base of the first leaf Fur- ther development varies accordingto the character of the aduitplant,whether tuberous, pseudo-bulbous or stem-forming. In tuber-forming or- chids, like our native Orchis (fig. 163), Ophrys and other Ophrydeae the first root lengthens rapid- ly and penetrates the ground vertically, gradu- ally drawing beneath the soil the growing germ- tubercle. The formation of the first tuber begins towards the end of the first season and is completed in the next. It arises as a semi-circular gi'owth within the tubercle below the terminal bud (fig. 163, C). With the second season the axis of the Fig. 163. A, Germ-tubercle of Orchis inili- taris in October, bearing the apical cotyledon, X 2. B. Similar stage in longitudinal section shewing vascular tissue passing to the coty- ledon. C. Later stage (also found in October) in longitudinal section ; a, first leaf which forms a sheath surrounding the successively overlapping follo^ving leaves, b, c, d ; 2, origin of first tuber. E. Seedling nest June, about 1^ nat. size. F. Lower part of same cut lengthwise, enlarged ; a, sheath; b, first foli- age-leaf; 1, germ-tubercle; 2, first tuber; g, its apical bud ; i, stalk. D. Similar stage in another species, the root-hairs have disap- peared from the germ-tubercle, which has been drawn beneath the surface by the contraction of the upper part of the root. The
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1904
