METAMORPHOSES OF INFLORESCENCES AND FLOWERS. 101 



Carpels. 



Useful Changes. — Wherever carpels change into any other organ they 

 of course lose their function of setting seed as in completely double 

 flowers, but if they become f oliaceous they acquire all the functions of the 

 leaves, as in the Green Rose, Double Cherry, &c. 



Useless Changes. — Besides the carpels being replaced by petals, it 

 sometimes happens that petaloid structures take the place of ovules. 

 Such occurs occasionally in Cardamine pratensis and betrays itself by the 

 fruit being globular instead of a long siliqua or pod. Again, stamens have 

 been known to replace ovules, but these metamorphoses are by no means 

 of common occurrence and are always abortive and useless structures. 



Sexual Changes. 



Useful Changes. — In plants with distinct sexesjin different flowers, 

 whether they be both on the same plant (monoecious) or on separate 

 plants (dioecious), female flowers may appear mixed with or in place of 

 male ones, and vice versa. Thus ripe grains of maize may be found 

 intermixed with the staminate flowers of a male panicle. So toe 

 female flowers sometimes occur on the male catkins of the Spanish 

 Chestnut. Conversely, anthers may occur in the female cones of Pines. 



In unisexual plants external conditions may bring about a change of 

 sex. Thus the males are usually borne by weaker shoots of trees, and 

 a greater preponderance of males among herbs appears when there is a less 

 amount of nourishment for all the seedlings growing thickly together. 



Useless Changes. — The last kind of changes attempted by stamens is 

 into carpels. This is not at all uncommon in certain plants. Thus in 

 all large growings of Wallflowers, as for market purposes, there will 

 generally be found "rogues " ; they do not open their flowers, the petals 

 being dwarfed and imperfect, while the six stamens are changed into 

 abortive carpels, often partially open or more or less coherent with the 

 pistil in the middle. They bear rudimentary but useless ovules. 



Oranges grown in conservatories often bear small rudimentary carpels 

 more or less coherent to the ovary at the base, and when this swells into 

 the fruit the " pistilloid " stamens form small orange-coloured projections 

 on the fruit. 



Poppies, again, not infrequently have a circle of little abortive carpels 

 round the base of the pistil They have arisen by metamorphosis of the 

 stamens.* 



* Other abnormalities will be found described in Dr. M. T. Masters'a Vegetable 

 Teratology. 



