10 INDUCTION, DEVELOPMENT, AND HERITACILITY OF FASCIATIONS. 



i:)recedes a rin,y;--fasciati()n, thon.t^h as yet no ring--fasciation was apparent. 

 In all wild (\ diciniis the stems'were infested with larvae below the fasciations 

 and the oTooves full of eallus, yet it was impossible to find intermediate 

 conditions. A plant with a fresh larval trail up the side fasciated after a 

 month of elons'ation from the rosette sta.y-e, but by the time the character 

 of the ti]) was well determined the first eft'ects were obscured by the later 

 <4-rowth. Unecpial formation of wood on the two sides at the base of fas- 

 ciated stems may be taken as an indication of local inhibiticjn. Transverse 

 sections of the lower, round part of branches, which are flat above, usually 

 reveal variations in the width of the woody rin.^-. The difference may be 

 slig-ht or, in a few cases, as in plate v, fig. 16, very marked and accom- 

 i:)anied by callus formation. In the g:roove -fasciations (plate iv, fi.Q's. l/^ 

 4/^) the width of the primary wood where it adjoins the g-roove, at xx, is 

 narrower than at .rr. This is also found to be true in sectioning- the rosettes 

 cut in late summer from the old stems (plate v, fig". 9). 



What has been said applies to plants out of doors. It seemed probable 

 that a different state of thing-s would hold in the gTcenhouse. Yet the 

 fasciated rosettes in the greenhouse have in the stems circular meristems 

 about brownish discolorations and a sig-nificant feature of their development 

 is one-sidedness of growth and a forcing- out of the axillary branches. 

 Rosettes of O. crnciata planted June 16, 1906, and kept in the g-reenhouse 

 during- the summer, were subject to such conditions in the pith. These, 

 like the rosettes of O. parviHora of 1905-1906, showed roug'h places on the 

 l^etioles and midribs of the leaves, incurling- of some of the leaves in the 

 g-rowing- tip, and ruffling- of the margins. The O. parviflora planted in 

 the summer of 1905, in December, showed larger and longer leaves. on one 

 side than on the other. There was then no sign of linear growth, but in 

 April they began to fasciate, and in May all four plants were fasciated. 

 Frequently the rosettes tip up, owing to the premature development of a 

 lateral branch (plate ii, fig. 4), so that one side is higher than the other. 

 This looks as if there were inhibition of growth on the concave surface. 

 The result of further growth is often a complete torsion of the fasciated 

 main axis with fasciation also in the side branches. In studying fasciation, 

 species with compact symmetrical rosettes are much to be preferred. O. 

 irrandiflora is among the impracticable forms, for the side branches normally 

 come out very early. A double rosette of Raimanuia odorata, a near relative 

 of the Oenotheras, the plant illustrated in text fig. 1 and in plate v, fig. 17, 

 when sectioned was found to have been injured below the bifurcation, and 

 at this point (.vx) there was inhibition in the formation of wood. Only the 

 bifurcated fasciations can be detected at the start, and these are of com- 

 paratively rare occurrence. It is evident, however, that the rosettes under 

 cover are not exempt from outside injury, and insects may readily enter the 

 greenhouse through the ojK'n ventilators, besides the man\' which habituall>- 

 live there. 



