=Viviparous plants.=--The spikelets of certain grasses are frequently found with some of their constituent parts completely replaced by leaves, like those of the stem, while the true flowers are usually entirely absent. A shoot, in fact, is formed in place of a series of flowers. In these cases it generally happens that the outermost glumes are changed, sometimes, however, even the outer and inner paleae are wholly unchanged, while there is no trace of squamulae or of stamens and pistils within them, but in their place is a small shoot with miniature leaves arranged in the ordinary manner. The grasses most commonly affected in this manner are _Dactylis glomerata!_, _Poa bulbosa!_, _Poa annua!_, _P. trivialis!_, _pratensis!_, _alpina!_, _angustifolia_, and _laxa_, _Cynosurus cristatus_, _Festuca nemoralis_, _F. ovina!_, _Glyceria fluitans!_, _Gl. aquatica_, _Aira alpina!_, _caespitosa!_, _Phleum phalaroides_, _Lolium perenne!_, _Alopecurus pratensis!_, _Agrostis alba_, _Holcus mollis!_ [Illustration: FIG. 81.--Portion of panicle of _Aira vivipara_ and separate floret.] From an examination of the structure of viviparous grasses Von Mohl was led to the conclusion that the lower palea is to be considered as a bract, and not a perianthial leaf, because the base of the palea surrounds the stem or axis of the spikelet entirely, and both its margins cohere towards its lower extremity.[159] A similar condition occurs not infrequently in _Polygonum viviparum_, and in _Juncaceae_, _Cyperaceae_, &c. In the genus _Allium_ an analogous formation of little buds or bulbils takes place in lieu of flowers; this is specially the case with _A. vineale_, the flowers of which are rarely seen. Other illustrations of a similar character, where the adventitious leaf-buds are mixed in amongst the flower-buds, are cited under the head of Prolification of the Inflorescence.