(317) 
lendons are differentiated, whose peripheral cells possess thin 
and permeable walls. 
n the Galieae Lloyd® reports cases analogous to that found 
by Koorders* in Zectonda. In Vaéllantia and Galium some 
of the cells of the suspensor elongate laterally to form haus- 
toria which penetrate the surrounding endosperm to a con- 
siderable depth, seemingly, as the author suggests, increasing 
the surface for absorption, and thus providing for a rapid 
growth of the young embryo. 
In some of the later researches the behavior of the pollen- 
tube has been carefully considered. Longo™ finds that in 
Cucurbita Pepo it follows a definite conducting tissue from 
the stigma to the embryo-sac. In the apical region of the 
nucellus the tube expands and sends branches into the sur- 
rounding tissues, the branching being correlated with the dis- 
tribution of starch in those parts. It is the thought of Longo 
that the growth of the pollen-tube along the conducting tissue 
is an expression of chemotropism, in which he is in accord 
with the views of Molisch. In different species of the same 
genus Longo shows that the pollen-tube may pass through 
the conducting tissues or on their surfaces in ovarian spaces, 
the stimulus being in the nature of asecretion. Lloyd found 
in Diodia and Aichardsonia that the pollen-tube was endo- 
tropic and ectotropic in different parts of the same ovary. He 
concludes that the behavior of the pollen-tube, whether ecto- 
tropic or endotropic, is a purely physiological character, and 
of no phylogenetic significance as interpreted by Treub and 
Nawaschin.* 
The growth of the pollen-tube toward the ovule and 
its ultimate arrival at the embryo-sac indicate either some 
mechanical relations (Miyoshi) or the differential distribution 
of the stimulant by which it may be directed chemotropically. 
That the source of this stimulant is either the oésphere or 
the synergids there is some reason to believe, and this view 
has already been advanced by Lloyd.® 
*See Lloyd: The pollen-tube in the Cucurbitaceae and Rubiaceae, 
Torreya, 4: 86-91. June, 1904. 
