2 MR. M. M. HARTOG ON CERTAIN SPECIES OF THUNEERGIA. 



Tracing out the development, we find the first sign of an axillary- 

 bud at the sixth or eighth pair of leaves from the growing-point; next, 

 on its hemispherical prominence form two elevations, a little above 

 the base. This latter becomes the pedicel ; the basal elevations 

 are the bractlets, and soon become crescentic, enlarge, and cover 

 in the apex of the bud. About this time, at the base of the pedicel, 

 the small elongated area between it and the now broad base of the 

 bract rises up in the centre to form a second bud, which develops 

 in the same way as the first. This process may be repeated four 

 or five times. Each young bud is at its origin lodged in a pit 

 hollowed out in the pedicel of its next elder sister bud, to whose 

 axis its own is at first parallel. 



I have observed fundamentally the same relations and develop- 

 ment in T. coccinea ; and, from dried specimens and figures, T. 

 grandiflora would come even closer to the type I have just de- 

 scribed. In T. erecta the mode of development is the same ; but 

 the plurality is not so constant, symmetry in opposite axils is not 

 invariable, and often the younger sister to a flower-bud is a vege- 

 tative shoot. In T. alata an&fragrans I have never seen more than 

 one younger sister bud. This originates early, but never develops 

 till after the flowering or even seeding of its elder sister-bud. 



The anatomical structure confirms fully the view that these 

 buds stand truly in the relation indicated by their development. 

 Each bud has its separate fibro- vascular bundle, which runs apart 

 from the others to join the " common bundle " bending outwards 

 from the stem along the node into the petiole *. 



As regards the floral development specially, I have always found 

 the calyx with five teeth, and the posterior one the largest, in the 

 youngest buds where there was any trace of this verticel ; and we 

 may conclude that the posterior sepal is the oldest. In T. lau- 

 rifoliaand T. coccinea (" calyce annulari truncato") all trace of teeth 

 disappears before the earliest outgrowth of the petaline and sta- 

 minal tubercles. But in T. erecta, &c, the five teeth may persist 

 till after the closing-in of the ovary, or may soon become incon- 

 spicuous : in the former case secondary teeth festoon the intervals 

 between the sepals, in the latter the ring becomes pluridentate ; 

 but, save for the posterior tooth, I have been unable to ascertain 

 satisfactorily the genetic relations between the numerous teeth 

 of the adult calyx and the five primary sepals. 



* I may here call attention to Ruellia Herbstii, which has the same plurality 

 of buds as Thunbergia laurifolia ; and moreover, the bractlets being fertile, each 

 bud develops into a true fascicle of three, seven, or more flowers. 



j 



