20 
ORGANOGRAPHY. 
BOOK I. 
if the tissue of Zamia be allowed to remain macerating fpr 
some time in dilute nitric acid, the apparent pores disappear : 
that is to say, the granules that cause the appearance of per- 
forations are dissolved. It has been thought that such ap- 
pearances as these were confined to Cycadeae and Coniferae ; 
but I suspect that they are far from uncommon in other fami- 
lies. Such tissue constitutes a considerable part of the wood 
of Calycanthus (Plate II. fig. 4.), as has been already noticed; 
and it is abundant in Bragantia. This kind of tissue might 
be called granular tvoody tissue : it approaches very nearly to 
the character of vasiform tissue, into which, in Zamia, it seems 
to pass by almost insensible transitions. It may, however, be 
known either by its very acuminated extremities, or by its 
granules not being arranged in a spiral manner. 
3. The third kind of woody tissue is the glandular. This 
has hitherto only been noticed in Coniferae, in which it is uni- 
formly found in every species. Its dimensions are more con- 
siderable than that of either of the last-mentioned forms; and, 
like the second, it has been described as perforated with pores. 
It differs from granular woody tissue in the markings of the 
tubes being vesicular, and usually transparent, with a dark- 
ened centre (Plate II. fig. 5, 6. 8.), which last is what has 
been described as a pore, the vesicle itself being considered a 
thickened rim. Kieser figures the glands as pores, both in Pine- 
4 5 wood (^g. 4.), 
and in Ephedra 
(Jig. 5.), and in 
other cases also. 
They may be 
most conveni- 
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ently found by examining a thin shaving of common Pine- 
wood (Pinus Strobus) with a microscope, when they will be 
seen in the form of transparent globules, having a dark 
centre, and placed upon the walls of the tissue. That these 
globules are not pores, seems to me to be proved thus : they 
are flaccid when dry, and distend when moistened, which is 
not the property of a pore; their centre is more generally 
opaque than transparent, which is also not the property of a 
pore ; they may be torn through the middle without any hole 
