g2 BOTANICAL GAZETTE [AUGUST 
in the lower half of the carpellary tissue, one or two sacs for each 
carpel. He interpreted the central parenchymatous tissue as a 
solid ovary, no special segments being differentiated for the pro- 
duction of ovules. 
We are indebted chiefly to TREUB (33) for an accurate account 
of the development and a clear interpretation of the reproductive 
organs of the Loranthaceae. He found in Loranthus sphaerocarpus 
that the tip of the floral axis grows up between the carpels, forming 
a mammilliform body, the ‘“‘mamelon,’’ which becomes united to 
them along their inwardly projecting margins. Between these 
lines of union with the carpels the “mamelon’’ is lobed. There 
are as many lobes as carpels, which are 3-5 in number. An embryo 
sac is formed in each lobe of the “mamelon.” TRevB interpreted 
these outgrowths of the ‘“‘mamelon” as rudimentary ovules, and 
the central region of the ‘““mamelon” he regarded as a placenta. 
He found in Loranthus pentandrus but a slight elevation of the floral 
axis between the carpels which he called a “rudimentary placenta” 
and in which the embryo sacs are formed. TREUB (35) described 
a still greater reduction in the floral parts of Viscum articulatum, 
in which there is no projecting placenta or ‘‘mamelon.’”’ The 
embryo sacs in this species arise from sub-epidermal cells of the 
sunken apex of the receptacle. Josr (15) described later a similar 
condition in Viscum album. 
According to JoHNnson’s (14) account of his observations on 
Arceuthobium Oxycedri, there is at the time of pollination a pro- 
jection of the floral axis which fills the entire ovarian cavity but 
does not fuse with its walls. He has shown that in opposite sides 
of this body two embryo sacs are formed, each of. which arises from 
a hypodermal cell. JoHNsoN assigns the same morphological value 
to the elongated axis that Treus did for Loranthus s phaerocar pus. 
He describes the anthers as sessile on the segments of the perianth 
and without vascular bundles. 
A few years later, PEIRCE (24), in his studies on Arceuthobium 
occidentale, confirmed JoHNsoN’s account of the morphology of 
el fruit. His observations together with those of YorK (43) on 
me : percent aoe are the most detailed which have been 
of the American Loranthaceae. 
