43 6 



FOURTH GROUP. SEED-PLANTS. 



in some species of Aloe, Car ex and Pandanus; spiral arrangements with smaller 

 divergences than \ are sometimes found, as in Musa ; in Musa rubra according to 

 Braun the foliage-leaves have a divergence of f , the bracts of T 4 T : in Costus the 



angle of divergence of the foliage-leaves is \ or \, &c. The axillary shoot of the 



D 



f 



A 



FIG. 361. Crocus vernus. A the tuberous stem seen from above, B from beneath, C from the side in longitudinal 

 section. The lines of insertion of the scale-leaves yyy are seen forming closed circles, and the axillary buds kk belong- 

 ing to these leaves ; b the base of the dead leafy and flowering stem, and by its side hk in C the new bud, from which 

 a new tuber and a new flowering stem are formed. D longitudinal section through the new bud ; nn its scale-leaves, 

 / foliage-leaves, A bract, / perianth, a anthers ; k a bud in the axil of a foliage-leaf. 



Monocotyledons usually begins with a leaflet which is generally two-keeled and has 

 its dorsal surface closely applied to the primary axis ; such a leaf for instance is the 

 upper palea in the flower of the Gramineae, which is itself a shoot axillary to the 

 lower palea ; where the leaves of the successive generations of shoots alternate in two 



rows it follows that an entire system of shoots may 

 be bilateral, and divisible by a plane which divides 

 the leaves into halves, as in Potamogeton and Typha. 

 The insertion of the scale-leaves and foliage-leaves, 

 and often also of the bracts (for instance of the 

 spathe which is so common), is usually either wholly 

 or to a great extent amplexicaul, and the lower part 

 of the leaf is consequently sheathing; there is an 

 obvious connection between this and the absence of 

 the stipules which are so common in Dicotyledons. 

 The scale-leaves, rudimentary arrested states of 

 foliage-leaves, and many bracts are reduced to this 

 sheathing portion, which in the foliage-leaves usually 

 passes immediately into the green lamina, though a 

 comparatively long and slender stalk occurs between 

 the lamina and the sheath in the Scitamineae, 

 Aroideae, Palmae and some other forms. If there is no stalk and the lamina and 

 sheath are sharply distinguished, there is often a ligule present at the point where 

 they meet, as in the Gramineae and Alliurn (Fig. 363). 



The lamina is usually entire and of very simple outline, often long and narrow 

 (ribbon-shaped), seldom roundish and discoid (Hydrocharis), or cordate or sagittate 

 (Sagittaria and some Aroideae) ; branching of the lamina is of rather rare occur- 

 rence, and appears either in the form of lobes united by a broad base, or less 



FIG. 362. A Ilium Cepa. Bud inside the 

 bulb after removal of the bulb-scales ; st the 

 broad short portion of stem in which the bulb- 

 scales are inserted. A shows the lamina at /and 

 the sheaths of the foliage-leaves at sh which are 

 still short. In B the outer leaves of A are re- 

 moved, and an axillary bud k" is discovered by 

 the side of the terminal bud k'. 



