MONOCOTYLEDONS. 



549 



the typical one for Monocotyledons, it will be seen that the great majority of 

 families the number of whose parts deviates from this type, do this only by 

 the suppression of single members or of whole whorls, the typical position of 

 those that still remain with respect to one another not being disturbed. The 

 variety in the forms of flowers in this class is therefore brought about almost entirely 

 by abortion^; and it is not uncommon for abortion to be carried to such an extent 

 in Monocotyledons that nothing is left at last of the whole flower but a single 

 naked ovary or a single stamen, as happens frequently in Aroideae. In these 

 cases a similar explanation of the relationships of the parts of the flower is 

 approached and elucidated by the occurrence of flowers with the actual typical 

 structure, and by a complete series of transitions caused by partial abortion. It is 



Fic;. 400.— Diagram of Alisniacerc ; .-i Butomus, B Alisina. 



Fig. 401.— Diagram of Triglochin (Juncaginea'). 



especially in small closely crowded flowers, as those of Spadiciflora^, Glumiflorse, &c., 

 that so great a reduction of the typical number of members is observed ; while in 

 larger and more isolated flowers the number of members in each whorl is usually 

 complete or even excessive (as Butomus and Hydrocharis), and deviations usually result 

 from petals (or petaloid staminodes) being formed in the place of fertile stamens 

 {e. g. Scitamineae). With reference to the abortion which is often carried to so 

 great an extent in small flowers, it may in certain cases even be doubtful whether 



Fir.. 402.— Diagram of Gymnostacliys (Aroidew), after Payer. 



in an assemblage of stamens and carpels we have a single flower or an inflorescence 

 consisting of several flowers reduced to a very simple state by abortion, as for 

 example in Lemna. 



When both the perianth-whorls are well developed, they are usually similar in 

 structure; in large flowers they are generally delicate and petaloid and either 

 brightly coloured or not (Liliacese, Orchide^, &c.); in small flowers on the con- 

 trary they are firm, dry, and membranous, as in Juncaceae, Eriocauloneoe, &c. 



Compare what was said on Abortion at p. 201 and in the Introduction to Angiosperms. 



