640 SCALE-LEAVES, FOLIAGE-LEAVES, FLORAL-LEAVES. 



the lobes of the blades whilst still under the ground are depressed as in Podo- 

 phyllum, but here the penetration is accomplished by means of peculiar bumps and 

 bladder-like protuberances on the uppermost lobes, which again consist of strongly- 

 turgid cells. In the Asarabacca (Asarum) it is the apex of the lower leaf folded 

 together lengthwise which is composed of turgescent cells, and which growing 

 upwards, presses the earth apart like a wedge. In the Broad-leaved Allium, Dog's- 

 tooth Violet (Allium ursinum, and Erythronium Dens Canis), in the Star of 

 Bethlehem and Hyacinth, and many other bulbous plants, also in numerous orchids 

 of our meadows and woods whose buds pass the winter embedded in deep soil, the 

 apex of the lowest leaf -blade is transformed into an actual ground-auger, usually 

 shaped like a hood or folded cap-like over the apices of the other leaf -blades of the 

 plant. A group of cells without chlorophyll is always found on the apex of that 

 leaf which envelops the others, and this apex may be plainlj'- distinguished by its 

 white colour. In most of the plants examined the cells are thin-walled but very 

 turgid; only a few present thickened walls, as, for example, the Broad-leaved Allium 

 (Alliuin ursinum), where the whole leaf -apex is almost horn-like. This group of 

 turgescent cells always forms the apex of the leaf-cone growing out from the 

 subterranean bud; afterwards when this cone has grown up, and the leaves are 

 spread out over the soil, the formerly tense cells of the leaf-apex collapse, dry up 

 and present a withered appearance. In the Asarabacca and in many orchids the 

 apices of the mature and lower leaves are regularly browned, and look as if burnt, 

 even when they have not been actually injured in penetrating the ground. 



The term floral-leaves comprehends all those which are directly or indirectly 

 concerned in the processes of fertilization, and in the production of the embryo. 

 First of all we have the leaf-structures within which the germ-cell is formed, that 

 cell from which the embryo proceeds after fertilization. Then there are those in 

 which arise the fertilizing cells known by the name of pollen-grains. Finally all 

 those which are concerned in bringing about the union of the pollen-cells with the 

 germ-cells, or whose task is to protect these two kinds of sexual cells during their 

 development from injurious external influences. Since the processes only shortly 

 indicated here will be fully described in the second volume of The Natural History 

 of Plants, and since the forms of the floral leaves will be considered in these 

 descriptions, we need not here give a detailed representation of these structures. 

 In the pages which follow they will only be treated of so far as is necessary for 

 the comprehension of the architecture of the whole plant, and of a series of 

 botanical terms. 



With regard to the succession and arrangement of floral-leaves, it has to be 

 noticed as one of their most characteristic features that the last and uppermost 

 floral leaves are always very close together, and are usually developed as closely 

 appressed ^vhorls. These assemblages of floral-leaves together form the flower. The 

 axis which bears the flower at its free end is termed the flower-stalk (pedunculus). 



The axis which is terminated by the flower is only in rare instances, viz. in a 

 few annual herbs, the direct continuation of the shoot which is produced from the 



