ETIOLOGY OF MALFORMATIONS 195 



Cruciferae through infection with Phytoptus ; they have the form partly 

 of abnormally shaped leaves, partly of varying states of doubling and 

 prolification of the flower. The modifications of the leaves are in general 

 of such a kind that fringes like the teeth of a comb are developed 

 upon lobes which usually project over the leaf-edge. In Centran- 

 thus Calcitrapa the condition called by Masters 1 ' enation from foliar 

 organs ' often appears. In the inflorescence of Cruciferae the bracts 

 which are usually entirely aborted appear below a few or many flowers, 

 and take on the form and texture of small foliage-leaves. The 

 doubling of flowers takes the most different forms. Every inter- 

 mediate stage from the petalody of single stamens and carpels to the 

 most complete doubling appears, and there may also be prolification, 

 tripling of the corolla, calycanthemy, and so on. All these conditions 

 were evoked by the introduction of a parasite, a Phytoptus, which was 

 found in degenerate buds of Valeriana tripteris. The degree of the trans- 

 formations caused by it varied according to the amount of infection and 

 the sensitiveness of the plant. 



Analogous phenomena are frequently produced both in the flowers 

 and vegetative organs of species of Juncus, such as lamprocarpus, supinus, 

 acuminatus, and others, by the prick of an insect, Livia juncorum 2 . The 

 appearances produced in the flowers vary according to the moment at 

 which the transforming influence of the insect affects them. Commonly an 

 arrest of the sexual organs occurs, but besides this there is sometimes an 

 enlargement of the perianth-leaves to quite three times their normal length, 

 sometimes there is bud-formation in the axils of the perianth-leaves through 

 which their position is changed, and in extreme cases a large tuft of leaves 

 may take the place of the flower. Vegetative shoots may also be changed 

 by the insect (Fig. 109) so that the internodes remain quite short and 

 lateral shoots with leaves arranged in a phyllotaxy of |- develop 

 in the axils of almost all the leaves 3 . The changes to which the leaves 

 themselves are subjected are however specially peculiar ; the vagina is 

 greatly enlarged whilst the lamina remains small or may be entirely 

 aborted 4 , in other words, the insect brings about here tJic same changes which 

 take place othenvise in tlic normal ' leaf-metamorphosis ' when a catapJiyll 

 or a liypsopliyll arises from the primordium of a foliage-leaf. The advantage 

 to the insect is that the soft tissue of the leaf-sheath attacked at the 

 period of elongation furnishes it more easily with food. 



1 Masters, Vegetable Teratology, p. 445. 



2 See Buchenau, in Abhandl. d. natunv. Vereins zu Bremen, ii. p. 390. This is one of the 

 commonest of malformations ; in the vicinity of Munich abundant examples may be found. 



3 This is not however regular and there is much torsion and displacement. 



4 These malformations ought to be studied by those botanists who in spite of the history of 

 development and other evidence will persist in regarding the leaves of the rush as shoots. 



O 2 



