notch being symmetrical to the external notch 27 a v mounting v shaped clamp 32 ties the frame 31 of the curved glazed panel 6 to the other opposite end of the mounting 29 which passes underneath the longitudinal beam 12 this v mounting 32 has a mounting bracket having one end secured to the ends of the tie beam 8 and a second opposite end this mounting 32 ties the two extremities distal panels of the span 7 the v mounting 32 has a second opposite end that is curved by a right angle at a middle portion thereof between the end portions thereof which engages itself in a notch 33 formed in the frame 31 of the curved glazed panel forming the bottom of the span 7 the lateral greenhouse wall 13 comprises a window and a overglazing joined by the elastic interlocking of their respective frame sections fig7 a and 7b are combined a cross section view with interruption of a movable span or a movable span portion 7 of a greenhouse as shown in fig2 which includes mobile portions 15 a fixed frame 34 of dimensions equivalent to those of the curved glazed panel 6 is fixed in the span the frame 34 is topped by a mobile curved glazed panel 15 of corresponding dimensions this frame 34 and this panel 15 are adjusted in a joint manner.