352 INDEX. 



Leaves of Dicotyledonous plants — their reticulated vascular 

 structure more complicated than in the Monocotyle- 

 dories 292 



thin or membranous, an examination of . . 293 



attached to the wood hy bundles of internal, spiral 



or sap vessels which enter the petiole . . . ib. 



The proper vessels pass only into the bark ; as il- 

 lustrated by the passage of colored fluids . . 294 



arrangement of the vessels in the transverse slice 



of the petiole of the Lilac ib. 



the disposition of the vessels in compound leaves 295 



the vascular structure of the petiole of the Holly- 

 hock and Geranium, nearly similar to that of com- 

 pound leaves ; a similar structure in the petioles of 

 some longitudinally ribbed or nerved leaves . 296 



vascular bundles in the lamina greatly subdivided, 



becoming smaller bv subdivision and the diminution of 

 their number, but not by any reduction of their re- 

 spective diameters 297 



do the vessels of leaves then anastomose, or are 



the smaller fasciculi merely separations from the larger? ib. 



in the smaller branches, many bundles of vessels 



are, however, connected nearly at right angles, and are 



not separations from the larger fasciculi . . ib. 



Leaves, thick and fleshy, of the dicotyledones examined 298 



part of the fluid taken up from the air, in those 



plants, passes probably at once into the central cells, 

 whose contents are colorless: — another undergoes the 

 usual change from light and aeration . . . 299 



Leaves, the cellular system of 300 



the cells, probably, originally spheroidal . . 301 



their hexagonal figure, the effect of mutual and 



coequal compression ib. 



their individual structure ; separated necessarily 



from each other by a double membrane . . ib. 



. the cells probably communicate with each other 



by pores, but the fact has not been demonstrated 302 



the cells sometimes contain crystallized salts 303 



vary in size ...... ib. 



their vascular and cellular system nearly similar to 



that of the stem 304 



Leaves, their culicular system, its uses and appearance 304, 305 



the epidermis not really perforated by pores, but 



enters into and lines them, and the real pores, though 

 existing, have not been rendered visible even by the 

 microscope ........ 305 



their interior culicular layer, consisting of a vascu- 

 lar net-work ib 



