330 Szabo .— The Development of the Flower of the Dipsacaceae. 
when the development of the cupular ovary of the ovule and of the 
involucel has been completed (PI. VIII, Fig. 29). 
During the development of the flower the bract plays an important 
part as a protector, thoroughly covering and surrounding the little bud in its 
boat-shaped cavity (PI. VIII, Fig. 2 3). While the bud is growing, the basal 
part of the bract grows too; its end bends over the top of the bud (PI. VIII, 
Fig. 24). The outer side of the petal-lobe, covering the bud and also the 
outer side of the bract, is generally thickly hairy ; or, if the latter is bare, 
then it has a red colour caused by anthocyan. During the blossoming the 
tip of the bract is bent back, but the lower part still surrounds the involucel. 
III. The Arrangement of the Vascular Bundles. 
Only the arrangement of the vascular bundles in the development of 
the flower, which are of importance in connexion with the morphological 
value of the ovary, will be considered. The joining of the vascular bundles 
has been determined by means of a series of longitudinal and cross-sections 
made with the microtome. The relations observed in this way have been 
compared with the situation of the vascular bundles in a typical tetramerous 
flower. 
For comparison I have figured the joining of the vascular bundles of 
a pentacyclic tetramerous flower with a superior ovary (Text-fig. 3). In Text- 
fig. 3, 1 the four leaves of the involucel, the four leaves of the calyx, the four 
petals, the four stamens, and the four carpels, situated alternately, are seen. 
The primary median vascular bundle of each has been indicated with 
a white circle. It is seen that the vascular bundles of the involucel, those of 
the petals, and those of the carpel are situated in the median-transverse line. 
The position of the vascular bundles of the calyx and of the stamens is 
diagonal. In the later drawings the flower-leaf whorls are seen to have 
been gradually inserted in the axis. In the axis first appear the four 
median-transverse carpel bundles (g ); the four bundles of the stamens (a) 
will soon be inserted between them diagonally (3). There are now eight 
vascular bundles in the cross-section of the axis and they have their woody 
portions directed inwards forming a ‘ eustele To the eight bundles of 
this eustele join the vascular bundles of the petals in the median-transverse 
line (g + e), those of the calyx in the diagonal line (a+fc), finally the 
bundles of the involucel in the median-transverse line (g + e + i). The 
result is that in the axis there are also eight procambial bundles forming a 
eustele. Later on, however, these eight bundles join to form a ring. This 
might be the course of formation of the procambial joining of the vascular 
bundles of a tetramerous flower theoretically, based upon the observations 
made on the Dipsacaceae. 
In the flower of the Dipsacaceae, however, the manner of union of the 
