74.S THE FLORAL STEM. 



this or that structure is useless, and to be intei'preted only as the remnant of an 

 organ which was developed more fully a long time ago in some ancestral species 

 to which it was indispensable. When we cannot immediately see the advantage 

 of any structure, we are not justified in saying that in its particular form it is 

 worthless or indifferent to the plant. The saying dies diem docet is perhaps 

 nowhere more applicable than to questions concerning the significance of forms. 

 How many structures which were enigmatical a century ago are now recognized 

 as essential members of very various contrivances, and explained in all their 

 details; their recognition being regarded as an incontestable scientific thesis! 

 The tendency of our age, indeed, is not merely to regard and describe forms as 

 mute puzzles of nature, but to comprehend their value as parts of a living entity. 

 Therefore I doubt not that sooner or later the importance of the different forms 

 of floral receptacles will find interpretation and explanation in the individual 

 species to which they belong. 



A peculiarity which distinguishes the floral receptacle from all other stem- 

 -structures, which has to be considered here in conclusion, is its limited growth. As 

 long as the receptacle forms floral-leaves on its periphery it always continues to 

 elongate to some extent, although the inci'ease in length is inconsiderable ; but 

 after the production of the highest floral-leaf no further divisions take place in the 

 cells of the apex, and the elongation of the axis is at an end, not temporarily, but 

 permanently. This fact is of importance inasmuch as one of the few differences 

 which have been established between stem and leaf undergoes a material restric- 

 tion thereby. But the limited growth of the floral receptacle has also a special 

 significance in regard to the architecture of the whole plant. The portion of 

 the stem which forms the floral receptacle separates usually with the flower- 

 stalk, and not infrequently even with the whole rachis of the inflorescence from 

 the floral stem below, as soon as the leaf-structures proceeding from the receptacle 

 have fulfilled their function; or, in other words, the flower and fruit-stalks become 

 detached as soon as the perianth-leaves have withered, the stamens emptied, and 

 the fruits matured — a process which reminds us of the detachment of those 

 foliage-leaves which are no longer able to fulfil their allotted tasks. Just as a 

 scar arises, or a withered stump remains behind where once a leaf existed, so a 

 healing tissue is formed at the place where a portion of the floral stem has 

 separated off, and at this spot no further stem growth takes place. If the 

 shoot terminates with a single flower, or an entire inflorescence, it can no longer 

 elongate in a straight line after the fruit has fallen; its apical growth is terminated 

 for ever. Lateral shoots, on the contrary, may spring from the axils of lower 

 foliage-leaves and may grow up beyond the scarred places, a fact which of course 

 materially influences the type of branching and the architecture of the whole 

 stem. This influence is very noticeable, especially in tall woodj' shrubs and trees. 

 Where for instance the scarred apex of a branch is overtopped by two lateral 

 branches springing close under the scar, a more or less regularly two-pronged 

 fork results; and when the process is repeated on the prongs of this fork, a very 



