species cvcntui'.llv "hreak tlH()Ui;li it, foiiu'mi; Mipcrticial oil vesicles,. 

 Anthrisciis and some B/ip/c/tr/n/is have neither oil-tiil>es nor 

 secreting cells. In Osniorhiza the matnre tVnit usually gives no 

 tiace of oil-tubes, while the iniinature fruit may show groups of 

 4 to () oil-tuhes in the intervals, and 1 to ){ in the ribs themselves. 

 Tile obliteiation of oil-tulies o)i approach to maturity may 

 account for the discrepancy of opinion concerning the oil-tubes of 

 certain genera. It is an interesting fact that this suppression of 

 oil-tubes seems to involve the formation of an oily layer. In 

 Osmorhiza the mature fruit has an oily layer about the seed, a 

 region occupied in the immature fruit by a distinct line of oil-tubes. 

 In IIydrocotyh\ however, the isolated groups of secreting cells 

 are such as always precede the formation of oil-tubes. In Hydro- 

 ro()'/6', therefore, the oil-tubes could be called rudimentary; in most 

 U/n be // if cnv they are oil-tubes proper; in Conium a secreting layer 

 has been developed ; while the development of the Osmor/iiza fruit 

 gives us distinctly all three phases. Hence, to summarize: (1) 

 most genera have distinctly developed oil-tubes, varioush placed; 

 (2) a few have a layer of secreting cells; (3) some have groups of 

 secreting cells; and (4) others have neither oil-tubes nor secreting 

 cells, in fact, without any representation of this one of the three 

 structures of the mesophyll. 



Strengthening ceils. Under this name we would define cer- 

 tain groups of cells which are imlike enough in structure, but 

 seem to serve the common purpose of strengthening the pericarp 

 wall or its ribs. They usually occur beneath each rib, and arc 

 normally developed about the simple fibro-vascular elements of the 

 pericarp wall. These fibro-vascular elements may eventually be- 

 come obliterated. The group of strengthening cells may consist 

 of fibrous tissue, sclerenchyma, sclerenchymatous parenchyma, or 

 small-celled parenchyma. It may be well marked off from the 

 surrounding tissues, as in the distinct thick-walled groups of 

 Osmorhiza., Cryptotivnia., Conium and C hcerophr /in w; or it may 

 gradually merge into the surrounding tissue, as in Ange/iccr., 

 Wiaspinm^ etc. In Hydrocotyic., Bowiesia^ Pastinaca., and 

 Heraclenni., the strengthening cells are developed in a broad con- 

 tinuous band about the seed-cavity, and so completely make up 

 the pericarp wall in Bifora and Coriandrnm as to make it crus- 

 taceous; while in Sanirnia^ Coniose/i/i/ini., and ^Kthnsa thev seem 



