28 THE TRUE GRASSES. 



is not removed) are very nourishing, but through later in- 

 vestigations this assertion has been brought into question. 



The so-called gluten layer is the outermost one 

 formed in the embryo-sac ; outside of it is to be seen a 

 generally indistinct, rarely very clear (Brachypodium and 

 Bromus) layer of cells, the remainder of the nucleus of 

 the seed ; outside of this is the testa, which has arisen 

 from the inner integument, the outer one having disap- 

 peared. Then follows the pericarp. (See above.) 



Means of Distribution. — In all wild grasses certain 

 parts of the spikelet or of the entire inflorescence fall 

 off with the fruit. If the spikelet is many-flowered and 

 every flower ripens its fruit, then its axis breaks into as 

 many pieces as there are fruits, and every piece carries 

 a floral glume and palea. If the spikelet is one-flowered, 

 the axis of the spikelet may separate above the empt}^ 

 glume, so that the floral glume and the palea fall off with 

 the fruit (Agrostece) ; or it may divide below the empty 

 glume, and the spikelet fall off as a whole (Pmricece, An- 

 dropogonece, etc.). If the spikelets form a spike or a 

 raceme, it frequently happens that the axis of the latter 

 divides, so that one spikelet falls off with each joint 

 (many Andropogonece and Hordece) ; short spikes (Triti- 

 atrn ovatum Godr.) fall from the culm as a whole. All 

 these arrangements are necessary for the distribution of 

 the seed ; they are lacking (with two exceptions) in all 

 cultivated cereals, but are present, on the contrary, in all 

 native races of the same species, so far as these are 

 known. Since these arrangements are very disadvan- 

 tageous for the complete gathering of the fruit, varieties 

 whose axes are less or not at all articulated will be pre- 

 ferred in culture, and will be finally fixed by natural 

 selection. 



The bracts surrounding the fruit act as a more 

 strongly developed pericarp ; they protect the embryo, 

 which is near the surface, from too rapid wetting, and 

 keep the soluble contents from being soaked out ; and 

 when it is once soaked through, they also protect it from 

 drying up again. But they are especially important as 

 means for distributing the fruit. They decrease the 



