100 BOTANICAL GAZETTE [AUGUST 
lobe opposite each of the three carpels. As development continues, 
these lateral outgrowths enlarge and grow downward along the 
sides of the axis. These lobes are the ovules. In direction of 
growth they are anatropous and do not become fused with the 
placenta along the side of which they grow. Only mere rudiments 
of integuments are formed, as has been already mentioned. The 
ovules are thus practically naked. The archesporial cells are sub- 
epidermal in origin. In Santalum album there is a conelike “mame- 
lon” quite similar to that in Thesium, but less extensively lobed. 
The ovules are without integuments. In Osyris alba naked ovules 
are found on a central placenta as in the two preceding examples, 
except the ovular lobes at first grow downward and then curve 
upward toward the apex of the placenta. 
From this comparison it is evident that TREUB’S interpretation 
of the “mamelon” is correct. The two lateral lobes of the elongated 
floral axis in Dendrophthora opuntioides and D. gracile are thus 
rudimentary ovules borne on a central placenta. The micropylar 
end of the nucellus is toward the base of the placenta, and the 
chalazal portion lies in the apical part of the floral axis (fig. 17). 
The vascular system of the flower 
One vascular trace passes from each of the three segments of 
the perianth into the inflorescence axis. A fourth vessel may 
enter the axis from near the base of the placenta, but there are no 
traces mn the placenta. The bundles within the segments of the 
perlanth as a rule never branch. About the time of the origin of 
the one-celled embryo sac, the cells just below the insertion of the 
similar in appearance to water-storage tracheids (fig. 19). This 
Plate of tracheids is analogous to the plate of collenchymatous 
tissue in Loranthus europaeus which HoFrMEISTER interpreted as 
being chalazal in nature. TReEvB has shown that a collenchy- 
matous body similar to that described by HormeisTER is present 
si ee Sphaerocarpus. During the formation of these short 
acheids, a series of longer tracheids appear in the outer wall of the 
Ovary at the level of the base of the placenta (text fig. 20, f). They 

