116 BOTANICAL GAZETTE | FEBRUARY 
action of the invading parasite. The presence of stomata on th 
stem and their absence on the scale leaves was pointed out, 
while the double circle of bundles traversing the flowering stem 
was peculiar in that the xylem of these faced each other. 
18. Water storage and conduction in Senecio praecox from Mens; 
Dr. Joun W. HarSHBERGER, University of Pennsylvania.—Senéti 
praecoz (Cav.) DC. is a composite plant inhabiting the vole 
canic beds of the valley of Mexico. It hasa cylindrical, succt: 
lent, woody stem rising three or four feet from the ground, with 
clustered deeply lobed leaves at the top. The plant storest 
an abundant supply of water in the pith, which is gradually used 
up during the dry season in Mexico, which lasts from October 
to June. The flowers develop in April at the expense of the 
reserve supply of water. Loss of water during the dry seasol 
is prevented by the fall of the leaves, and by protective cork 
and balsam, the latter secreted in the exocortex and endocortes: 
The water, stored in turgid disks of pith, is gradually conducteé 
by the woody cells and tracheids which penetrate into the 
medulla by wedge shaped ingrowths, representing the prima 
bundles, to the growing point where it is used. That this is th 
case is shown by the dry parchment-like pith membranes whi : 
were left in a piece of a stem which had remained in the dy 
state for over sixteen months. Conduction of water i ths 
stem was accomplished without assistance of root pressure; 
without any appreciable influence on the part of the small aa 
leaves in drawing up the liquid by aid of the transpiratit 
current. 
©) 19. Notes on the embryology of Potamogeton: MR. K. M.W 
GAND, Cornell University.— Potamogeton pauciflorus Was _ 
with reference to the origin and development of the emp 
sac, fertilization, and development of the embryo. The emo)" 
sac was found to arise in the usual manner for noe 
ledons, viz., from the subepidermal cell after the cutting 
of a tapetal cell. The egg apparatus and antipodals 
