Morphology of the Citrus. 213 



have passed several years in examining citrus fruit and 

 leaves of numerous varieties, and at all stages, not to 

 come to the conclusion that all I said justifies the 

 quotation given at the head of this chapter. This 

 frequent pondering of course may have the dis- 

 advantage of producing what the French call idtes 

 fixes ! 



NOTE. The " Physiology of Plants," by Jul. Von Sachs, p. 183, 

 gives the following : " The internal glands in the skin of the fruit of 

 the orange are very conspicuous and large ; they abound in ethereal 

 oils, and appear in transverse and longitudinal section, as roundish 

 cavities, from which the inflammable ethereal oil spurts out, on the 

 application of pressure. Such glands originate, so far as investiga- 

 tion extends, from a single mother cell, which, as it slowly develops, 

 undergoes many divisions in all directions, so that a multicellular 

 mass of tissue of roundish form arises, the cells of which subse- 

 quently become remarkable as containing very granular, apparently 

 dead protoplasm. Later on, the thin cell-walls dissolve ; the pro- 

 cess commencing in the middle of the spheroidal group and proceed- 

 ing outwards. There thus arises a roundish cavity filled partly with 

 watery sap, partly with drops of ethereal oil or balsam the pro- 

 ducts of solution of the mass of cells. The layers of tissue sur- 

 rounding this cavity fit closely on all sides, without intercellular 

 spaces, and thus form a kind of wall to the receptacle for the secre- 

 tion (well seen in the leaves of the Citrus)." 



Is there much in this genesis of the oil-cell, which differs from 

 that of an ovule, whether vegetable or animal ? E. B. 



