T. Holm — Croomia patwiflora. 53 



only one peripheral layer of collenchyma and the stereome is 

 reduced to a few isolated cells on the leptome-side instead of 

 forming a closed ring around the bundle. The mestome- 

 bundles themselves occur in a smaller number, from eight to 

 nine, and are strictly collateral ; they border on a narrow cen- 



Fig. 1. Transverse section of a mestome-bundle from the stem above 

 ground ; 500 x natural size. 



tral cylinder of pith. A corresponding structure is to be 

 observed in the peduncle of the flower, but this possesses only 

 two mestome-b undies, both of which are collateral. 



The leaf. 



The petiole : About three almost continuous, subepidermal 

 layers of collenchyma surround the thin-walled cortex in which 

 only a small amount of chlorophyll was observed. There is no 

 stereome and no endodermis is differentiated. Seven collateral 

 mestome-bundles traverse the petiole ; they are arranged in a 

 crescent corresponding with the outline of the petiole, and the 

 mediane is the largest. 



The blade : A thin smooth cuticle covers an epidermis with 

 the outer cell-walls slightly thickened on both faces of the leaf- 

 blade ; the stomata are level with the epidermis and they are 

 not parallel with the longitudinal axis of the blade ; they occur 

 only on the lower face. The chlorenchyma consists of live 

 homogenous layers of oblong cells, which are not perpendicu- 

 lar, however, on the leaf-surface ; this tissue is a little more 



