1784 



TERATOLCMtY 



TERATOLOGY 



known examples. Tlir ,gall-;rn:iTs among the true flies; 

 (Diptera) also product' a large variety of maifornia- 

 tions, of wijic-h the one-like galls resulting from de- 

 formed bmls of The willow and the goldenrod art^ best 

 known. Plant lice (Aphidae) are responsilile for the- 

 large smooth red galls on the petiole of sumachs, and 

 for the flattish serrated galls on elm leaves. The fusi- 



2484. Dahlia leaf, illustrating the branching of leaves. 



form giills on stem of goldenrod and asters is cau<^ed 

 by the larva of a moth. In addition to true insects, tin- 

 mites produce almost as great a varietv of u::iUs pouch- 

 galls and leaf-rolling bein-- r-sp. ■,-!:, llv .-.msi.jrTious. T)]c 

 cans.-, of these deformities i. .nii.ptinips th,. chemical 

 stimulus produced bv the injrrrin,, of ^utistance^ 

 ("poisons ") at the time of et:^'-lavini: bv rli.- parent in 

 which case the gall develops aroiiihl the etrL--; snjuHi i,lips 

 :t is tlie mechanii-al sfiujulus ,]u.- to iiiMVHUH.Tits nf tli-^ 



2485. Toad-flax- Linaria. 

 Showina normal ami ab- 

 normal flowers. Example of 

 Ijeloria. 



larva, together with the chemical stimulus from its va- 

 rious exci-etions, in which case the gal! ilevelops after 

 the hatching of the egg. 



0. jGninchhifi of heaves is 

 not infrequent, and its cause 

 is unknown. " F<:>ur-]eaved " 

 clovers otfer well-known ex- 

 amples, and the normal num- 

 ber of leaflets is often in- 

 creased to six or even mcu-e. 

 Fig. 24yi illustrates leaf- 

 branching in tlie dahlia. 

 Branching in the plane of 

 flattening, both in foliage 

 leaves and petals, has also 

 been observed, and the 

 branch described as an "out- 

 growth." 



(J. PeJorla . When usually 

 irregular flowers, sucli as 

 those with some spurred or 

 saccate petals or sepals, de- 

 velop all the parts of each 

 set alike, thus becoming 

 radially sj'mmetrical, the 

 phenomenon is called pe- 

 loria. It was first observed 

 by Linnjeus in Liimria vul- 

 garis, Fig. 2485, and the term 

 peloria, derived from the 

 Greek word for monster, 

 was given by him. Flowers 

 often become peloric on ac- 

 count of changes in their re- 

 lations to light, but other causes certainly cooperate. A 

 reverse change, by wbi.di radial flowers become zygo- 

 morphic, occurs in many Composit^e when the corollas of 

 disk florets become strap-shaped, as in the cultivated 

 asters and chrysanthemums, but no notice seems to 

 have been taken of it as a malformation. Sometimes 

 all spurs fail to develop. Figs, 246(.)-7. 



III. Traxsfoematiox of Organs: /. c, alterations 

 more profound than those of form, whi(di result in the 

 production of organs different from those which 

 normally occupy the position; often called metamor- 

 phosis. (The term substitution would be preferable at 

 present, because non-committal as to processes and 

 causes.) It is common to speak of progressive and 

 retrogressiv:? metamorphosis, 

 but these terms involve as- 

 sumptions as to the origin ot 

 foliage leaves and floral I'arts 

 which are not justifiable in 

 the present state of knowl- 

 edge. Transformations occur 

 chiefly in the region of the 

 flower, though they are not 

 found exclusively there. Ex- 

 amples are to be found in the 

 development of 

 leaves or leaf- 

 lets as tendrils 

 (Fig. 5041; of 

 sepals as petals; 

 and of petals as 

 stamens or jds- 

 tils. These 

 transformations 

 are usually mnre 

 or less iui])rr- 

 feet. On the 

 other hand, tiie 

 pistils and sla- 

 nieiis often de- 

 vehip as petals 

 (Fig. ;5(;7). and 



manv 



ui I 



Lack of spurs in the columbine. 

 Compare Fig. 2487. 



2486. 

 f I o \\"e r s owe 

 their f u 1 n e s s 

 chiefly to su'-li transformations, though other changes 

 nuiy ciiperate as noted above. Fig. 2488. Petals 

 may develop as sepals, bracts, or even imperfect foliage 

 leaves, while sepals and bracts fre*pu_-ntly become foli 



