1915] AASE—M EGASI YLLS OF CONIFERS 307 
(figs. 183, 186). At the base of the ovule each bundle passes into 
a mass of short irregular tracheids of large caliber. From each 
mass arises a small strand consisting of poorly developed xylem 
soon replaced by elongated thickened cells without xylem markings. 
Each strand passes upward in the thickened ridge of the ovule. 
Discussion 
Assuming that the megasporophyll in all the forms is a com- 
posite organ, consisting of bract and axillary scale, the investigated 
forms may be divided into four general groups based on the relation 
of bract and scale to one another. 
In the first group the bract and scale are separate almost to the 
base of the appendage and both are about equally prominent. 
Here belong Keteleeria (fig. 36), Pseudotsuga, species of Abies, and 
species of Larix. 
In the second group the bract and scale are separate as in the 
first group, but the bract, at least in the later stages, is much 
less prominent than the scale, and in certain instances appears 
distinctly to be on its way to obliteration. In this group belong 
species of Abies (2), species of Larix, Tsuga, Picea, Pinus (figs. 1, 2), 
and species of Podocarpus and Dacrydium (4); Cedrus Libani (2) 
and the lower sporophylls of Pinus Banksiana (fig. 2) show the 
bract in process of extinction. In species of Podocarpus the scale 
has folded toward its dorsal side, thus forming the second integu- 
ment or epimatium of the inverted ovule (fig. 182). 
In the third group the bract and scale are considerably to com- 
pletely welded, but the fused structure shows some evidence of 
its double nature. Within this group are Sciadopitys (2), Sequoia 
(2), Cunninghamia (fig. 139), species of Arthrotaxis (1), Cryp- 
tomeria (fig. 114), Taxodium, Thuja (fig. 85), Cupressus (fig. 59), 
Chamaecyparis (fig. 102), Juniperus (fig. 113), Araucaria (fig. 153), 
and Podocarpus dacrydioides (4). In young strobili of Araucaria 
Rulei (fig. 161) and Cryptomeria japonica (fig. 126) the bract and 
scale are distinct almost to the base, and the fused portion becomes 
comparatively large in the subsequent development of the organ. 
In Cupressus Benthamii (fig. 58), Thuja occidentalis, Chamaecy paris 
Lawsoniana (fig. 103), and Juniperus communis the scale in the 
