STRUCTURE, MORPHOLOGY, AND PHYSIOLOGY. 17 



which always stands in the median plane of the spikelet 

 towards the front. It is composed of an ovary with one 

 ovule and 1-3 st}des, each with one stigma ; the stigmas 

 may also arise from a single style or directly from the 

 ovary. If but one style with one stigma is present, it cor- 

 responds to the midrib of the carpel, and is to be regarded 

 as the blade, and the ovary as the sheath {Nardus). Many 

 times an aj)parently simple style arises from the union 

 of two (Zea, EuchLcena, and many species of Pennisetum). 

 If there are, as is by far the most frequent, two styles or 

 two sessile stigmas, they are lateral, never posterior, being 

 either on the sides or the front of the carpel. Both may 

 be regarded as the developed side portions of one lamina 

 (or blade), the central part of which is at the same time 

 suppressed ; they are therefore analogous to the anterior 

 lodicules. If the middle portion is developed, we have 

 the three (free or partly grown together) styles of many 

 Bambusece and Streptochceta, where the third st}de con- 

 sequently lies in front. In many pistils (Briza media ) 

 there is frequently a rudiment of a posterior style (often 

 provided with a stigma) which may be explained as a 

 commissural form like the ligule of Melica uniflora Retz., 

 which is opposite the blade and rises from the united 

 edges of the sheath. The stigmas, easily recognizable 

 by their papillate cells, are rarely simple (barbellate) 

 (Tigs. 73, 74:), but are usually spirally branched ; in the 

 latter case the branches either come off in all direc- 

 tions — aspergilliform (Figs. 15, 18), — or only from two 

 sides — plumose (Figs. 80, 89, 95). From these branches 

 rise smaller papilla?. The entire system of branches 

 has of course a large surface, and is especially arranged 

 to catch pollen carried by the wind. 



Pollination. — As has been stated, grasses are fertil- 

 ized by the wind. Monoecious and dioecious species are 

 not numerous ; but not a few are polygamous (many 

 Andropogonece and Pam'cece), and in these the $ flower of 

 a spikelet always blooms later than the hermaphrodite, 

 so that its pollen effects cross-fertilization upon the 

 stigmas of other spikelets or other individuals. There 

 are also many arrangements for cross-fertilization 



