Holm, Some new anatomical characters for certain Gramineae. 103 



Characteristics of the double parenchyma-sheath. 



In a transverse section of the leaf of the grass above named 

 the mestome-bundles are seen to be surrounded by one or, some- 

 times, tv^'0 layers of palisades, arranged radially around them. 

 These palisades border inwards on a closed sheath of thin-walled 

 cells filled with Chlorophyll. This encloses another sheath of 

 larger cells, with slightly thickened walls and with the same Con- 

 tents as the outer one (S in figure 1). Inside these sheaths are 

 the leptome and hadrome of the same structure and disposition 

 characteristic of the Gramineae in general. The mestome-bundles 

 are, thus, surrounded by two very distinct sheaths (P and S in 

 fig. 1), the cells of which are round in outline as seen in trans- 

 verse sectionS; and they both contain Chlorophyll, which as to 



M 



1. Fig. 2. 



Fig. 1. Tiaiisverse section of a small mestome-bundle of ilrw/t Jo /a«cjcMZa<a ; 



P = tlie outermost parenchyma-sheath; S = the inner pai-enchyma- 



sheath; L = leptome; M = thickwalled mestome-parenchyma; 



V = Vessels. 84ii X natural size. 



The chlorophyll-grains have been omitted. 

 Fig. 2. Longitudinal section of the double parenchyma-sheath; letters aa 



above. 744 X nat. size. 



color and relative size of grains, does not differ from that, con- 

 tained in the palisades. Viewed in longitudinal section (fig. 2) 

 both sheaths appear to be parenchymatic, somewhat stretched, 

 but with almost horizontal cross-walls. In this particular the inner 

 sheath departs from the structure characteristic of a mestome- 

 sheath, as this term has been applied by Prof. Schwendener 

 to certain internal sheaths, which occur in a number of Gramineae. 

 Moreover the testing with concentrated sulphuric acid did not 

 give the result, usually obtained in cases where a mestome- 

 sheath is developed. While thus the mestome-bundles of Aristida 



