VASCULAR SYSTEMS OF FLORAL ORGANS. 153 
by several observers *. Moreover, with regard to Van Tieghem's 
work, it is more especially the pistil to which he paid attention, 
at least in his first paper; though he subsequently treated of 
the anatomical details of the other organs of several flowers. 
The present contribution does not pretend to be exhaustive, 
butis an endeavour to open up a comparatively new field of obser- 
vation; for I am convinced that it will enable us to advance some 
way nearer to the solution of several morphological problems, if 
it do not actually solve the difficulties which have beset the inves- 
tigations of floral structures. 
PEDUNCLES AND PEDICELS. 
Before treating of flowers, some remarks may be made on the 
axes of inflorescences. The anatomical details observable in them 
contain several points of interest. Thus, while one is accustomed 
to recognize a single and symmetrical circle of cords round a 
central medulla as characteristic of exogens, and an irregular 
distribution as the peculiar feature of endogens, pedicels reveal 
the fact that these arrangements can be reversed, and that the 
exogenous type is frequently to be found in endogens and vice 
versá. Thus, many pedicels of Endogens with six leaves to their 
perianths have six cords as symmetrical in position as those of 
Exogens. On the other hand, some exogenous plants may closely 
resemble certain endogenous ones in the arrangement of their 
cords. Thus, Anemone (rt. 1; Pl. XXIII.) has a double circle 
of cords surrounding a lacuna in the medulla exactly like the 
peduncle of a Daffodil ; while the pedicel of the Apple (xxıv.1; 
Pl. XXVII.) closely resembles an ordinary endogenous stem. 
Another point of resemblance lies in the supportive tissues, 
namely, in the prevalence of pericycular sclerenchyma forming a 
cylinder outside the cords. The endoderm is not often distin- 
guishable, though its position may be occasionally presumed from 
the localization of starch, and is recognizable in some orders, as 
the Caryophylleæ, and in Lonicera &c. If a flower be pendulous, 
it is usually because the pedicel is more or less deficient in this 
supportive tissue where the flower-stalk bends. The stiff wiry 
* See “On the Floral Conformation of the Genus Cypripedium,” by Dr. M. 
T. Masters, Journ. Linn. Soc. vol. xxii. p. 402; also Prof. E. Pfitzers ‘ Mor- 
phologische Studien üb. d. Orchideenblüthe, Heidelberg, 1886. 
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