PHANEROGAMS, 
pits and hence with a more or less scalariform wall are very much like the long prosen- 
chymatous vessels of Vascular Cryptogams ; and this resemblance extends even to 
the tracheides of Coniferae, so far as they are distinctly prosenchymatous, although the 
smaller number and round form of the bordered pits shows a more marked difference. 
The bordered pits of Coniferae are usually developed only on the wall which faces the 
medullary rays, in one or two rows, but in Araucaria in larger numbers and densely 
crowded. In the structure of the secondary wood, as in that of their flowers and 
in their habit, Gnetacese approach Dicotyledons ; in Ephedra broad vessels occur in 
it together with the usual tracheides in the inner part of the ring of wood, but their 
component cells are separated by oblique septa, and are therefore still prosenchymatous, 
and are penetrated by several roundish holes ; their lateral walls show bordered pits like 
the tracheides, and furnish a striking evidence that the true vessels in the secondary 
wood of Dicotyledons are connected by intermediate forms with the vessels of Vascular 
Cryptogams formed from prosenchymatous cells. In the wood of Welwitschia tracheides 
with doubly bordered pits are also present. 
The medullary rays of the secondary wood of Coniferse are very narrow, often only 
one cell in breadth ; the cells are strongly lignified, and then* lateral faces in contact with 
the adjoining tracheides are provided with closed bordered pits. In Cycadeae the rays are 
broader, and their tissue bears a closer resemblance to the parenchyma of the pith and 
cortex ; their number and width cause the whole substance of the wood to appear spongy, 
and its prosenchymatous cells are seen to be strongly curved in different directions in 
tangential sections. The phloem-portion of the fibro-vascular bundles of Gymnosperms 
resembles that of Dicotyledons ; it is mostly composed of true strongly-thickened bast- 
fibres, cambiform cells, latticed cells, and parenchymatous cells ; while in Coniferae they 
are formed in alternate layers. Usually the soft bast predominates. 
The Fundamental Tissue of the stem of Gymnosperms is separated by the ring of wood 
into pith and primary cortex. Both are very strongly developed in Cycadeae, especially 
the pith, and consist of true parenchyma, while the woody portion is considerably 
smaller. In Wehvitschia the parenchymatous tissues appear also to predominate ; but 
the greater part of their substance is the product of the activity of the meristem-layer of 
the stem already mentioned. A large number of so-called spicular cells occur dispersed 
in all the organs of this remarkable plant, they are fusiform or branched and greatly 
thickened ; and a number of beautifully developed crystals are found imbedded close to 
one another in their cell-wall. Similar structures also occur in Coniferae (p. 66). 
The parenchymatous fundamental tissue of Coniferae decreases greatly with the 
increase in age of the stem (and of the root). With the exception of the pith, which is 
here small, the stem consists exclusively of the products of the cambium-ring, since the 
primary cortex, and afterwards also the outer layers of the secondary cortex which 
always have a subsequent growth, are used up in the formation of cork. In the stem of 
Cycadeae, the increase of which in thickness is inconsiderable, the formation of cork is 
also very small ; in Wel^itschia it appears to be entirely wanting (?). 
Intercellular Passages are widely distributed in Gymnosperms ; their structure is that 
which has been explained generally at pp. 78 and 94. In Cycadeae they are found in all 
the organs in large numbers, and contain gum, which exudes from incisions in thick 
viscid drops; in Coniferae they contain oil of turpentine and resin. In this latter order 
they occur in the pith of the stem, in the whole substance of the wood, and in the 
primary and secondary cortex, as well as distributed through the leaves ; always 
following the direction in length of the organs, like the gum-passages of Cycadeae. 
In many Conifers with short leaves roundish resin-glands also occur in them (as in 
Callitris, Thuja, and Cupressus, according to Thomas) ; in Taxus the resin-canals are 
entirely wanting ^. 
1 [Van Tieghem (Ann. des. Sei. Nat. 1872) distinguishes the six following modifications of the 
distribution of the secretory organs in Coniferse: — r. No canals in the root nor stem: Taxus. 2. No 
canals in the root ; canals in the cortical parenchyma of the stem : Cryptomeria, Taxodium, Podo- 
