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the Embryo and Seedling in the Gramineae. 
The examination of monocotyledonous seedlings with a well-developed 
upper sheath shows that this sheath does not always contain vascular 
tissue. Among the species that do, we find two forms of vascular skeleton. 
The bundles entering the upper sheath may be branches from those which 
pass from cotyledon to hypocotyl, and then they end blindly near the top 
of the sheath ( Colchicum ). Or the bundles from the cotyledon may them¬ 
selves enter the sheath, and after a longer or shorter course within it, turn 
down through the lower sheath to the axis [Elettaria, Commelina , Tigridid). 
We have described many more examples of the second form than of the 
first, because the second approaches the imaginary type X from which 
the vascular skeleton of the coleoptile can be derived. In particular, this 
form of sheath is found in several genera within the Zingiberaceae. 1 We 
may conclude that this form of vascular skeleton is inherited from some 
ancestor common to at least some of the genera within the Zingiberaceae. 
This is the more probable, as the structure of the first node and hypocotyl 
is also fairly uniform in these genera. 
The resemblance between the embryo of Canna and that of the 
Grasses, already pointed out by Hegelmaier (Y 4 , p. 669), is interesting 
in this connexion, since the Cannaceae are closely related to the 
Zingiberaceae. 
The geographical distribution of the Zingiberaceae indicates that it is 
an ancient group, 2 and the type of seedling skeleton which is primitive 
within it probably goes back to an early form of Monocotyledon. This 
makes the resemblance to the skeleton of Grass seedlings more suggestive, 
particularly as the likeness extends to first node and hypocotyl. 
Schumann points out the remarkable similarity in vegetative characters 
between the Zingiberaceae and the Gramineae, 3 but he does not therefore 
assume any genetic connexion. The Scitamineae on the one hand, 4 and 
the Glumiflorae on the other, 5 are generally considered as natural divisions 
of the Monocotyledons, without clear affinities to other groups. Both are 
probably related to the Liliiflorae. 6 
Even if no simple degree of relationship thrpugh a common ancestor 
should be discovered to explain the characters which the Zingiberaceae have 
in common with the Gramineae, it does not therefore follow that the sheath 
structure of one group may not illustrate that of the coleoptile in the other. 
More than one descendant from the prototype of the Liliiflorae may have 
stiffened its upper sheath by the entrance of whole bundles from the sucker 
1 In the six we have cut, the only exception is Brachychilum, in which the sheath contains no 
vascular tissue at all. 
2 Schumann, K.: Engler’s Pflanzenreich, iv. 46 ; Zingiberaceae, p. 27, 1904. 
8 Schumann, K.: 1 . c., p. 3. 
4 Petersen, O. G. : Engler’s Pflanzenfamilien, ii, Abth. 6, p. 38, 1889. 
5 Hackel, E.: Engler’s Pflanzenfamilien, ii, Abth. 2, p. 16, 1887. 
6 Wettstein, R.: Handb. d. syst. Bot., Aufl. 2, p. 782, 1911. 
