274 NATURAL SCIENCE. April. 



brownish scales called glumes, the number of which varies in different 

 genera. Each flower is solitary, or more often several are crowded 

 together forming a spikelet, while the spikelets may be arranged 

 closely forming the so-called " spike " as in wheat and barley, or 

 loosely as in the " panicle " of the oat. 



In each flower the stamens and pistil are generally ripe at the 

 same time and thus self-fertilisation is favoured. The barley is an 

 extreme case, as here the fertilising pollen escapes from the stamen 

 and falls on the moist receptive stigma of the pistil before the flower 

 opens and while the ear is still within the sheath. Wlien the stigmas 

 are finally pushed out beyond the scales of the flower they are dead, 

 and cross-fertilisation is therefore precluded. In the wheat the 

 anthers are already burst and some of the pollen-grains discharged 

 and adhering to the divisions of the ripe, feathery stigma before the 

 flower naturally opens, showing that self-fertilisation is at any rate 

 possible. The flower opens for a short time, about a minute, the 

 opening being effected through the pressure of the stamens, stigmas, 

 and the two small scales, or lodicules, supposed by some to represent 

 the petals ; the filaments pushing the anthers before them extend to 

 three or four times their former length, and the feathery stigmas 

 spread to the air. The pendulous anthers are shaken by the least 

 breath of air and rapidly emptied of their remaining pollen-grains, so 

 that the transference of pollen from one plant to the stigmas of the 

 flowers of another is also rendered possible. Observations in the 

 field show, however, that self-fertilisation is the rule, for in experi- 

 mental grounds where different varieties of wheat are grown in close 

 proximity in parallel rows, no accidental cross-fertilisation due to 

 wind-carried pollen-grains has been noticed. 



Artificial cross-fertilisation of wheat or barley is a delicate 

 operation. The parts of the flower are small, and the slender stamens 

 must be removed before the pollen is ripe, while the stigmas must be 

 protected from the access of pollen from outside. The application 

 of the selected pollen to the feathery stigma is best accomplished by 

 applying the ripe grains direct from the anthers to the stigma by 

 gently moving them over its surface. Moreover, this has all to be 

 done in the open field on a flower supported on a long, slender, and 

 easily-moved straw. 



The offspring obtained by cross-breeding vary in fertihty with 

 the closeness of affinity between the two parents. By fertilisation 

 with pollen from the flower of a similar plant of the same species, or 

 even of a plant with characters distinct and permanent enough to be 

 recognised as a variety, though still of the same species, we obtain 

 offspring producing fertile seeds from generation to generation. 

 When the pollen applied is taken from an allied species of the same 

 genus, perfect seeds can generally be obtained, but the hybrid plant 

 of the next generation is almost always sterile, though the vegetative 

 organs, such as leaf and stem, are often finer. In the case of widely- 



