10 MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE, 
are rarely auricled, and the blades often glandular-punctate. The blade is either 
obscurely or conspicuously nerved and rarely three-ribbed, and in one or two instances 
it has two lateral impressions parallel with the midrib. Very rarely, too, we meet with 
a keel on the under surface, as in the case of P. Paronychia. Towards and in the inflor- 
escence the leaves are sometimes reduced to foliaceous bracts, and all are subtended by 
stipules in the form of sheaths or ocreae, to which they are articulated or with which 
they are continuous. The stipules are of unusual form and characteristic. They are 
united so that they form a sheath which surrounds the stem for a greater or less distance 
above a node. ‘These ocreae are either cylindric or funnelform; the former usually hori- 
zontally truncate at the summit and the latter é6blique or two-parted. The summits may 
be either naked or variously fringed with bristles, and in two subgenera a spreading, 
eollar-like rim is found. The ocreae are either glabrous or strigose, sometimes with 
smooth or ciliate ribs and rarely with a ring of more or less reflexed hairs around the base. 
The inflorescence is both axillary and terminal, appearing as clusters, spikes, ra- 
cemes or spicate racemes. These different forms may be solitary, geminate, or paniculate 
and erect or drooping. Ocreae or more or less bract-like ocreolae subtend the flowers, 
which are borne on usually fascicled, jointed, erect and stout or deflexed and often slender 
pedicels. The subgenus Durayia is the only group in which the flowers are normally 
solitary at the nodes and in which the inflorescence is what we may call spicate. There 
are two interesting points suggested here. First, the phenomenon of cleistogamy, and 
second, fertilization. Little has been written on the former subject. Flowers may be 
produced on the roots as in the case of P. punctatum,' or they occur within the ocreae in 
certain species, as shown by P. Hydropiper® and species of other subgenera.* This latter 
kind of cleistogamy appears in two different ways. In consequence of the morphology of 
the plants of this genus, it is liable to occur in any species as illustrated in P. Hydropiper. 
On the other hand, as in the case of members of subgenus Duravia, it is the normal con- 
dition. Many interesting facts concerning fertilization have been recorded.* Both close 
and cross-fertilization are common in the genus. The flowers of different species vary 
in their structure and have adapted themselves as their environment directed. Some 
have fragrant flowers with eight nectaries, situated at the base of the stamens, which se- 
crete an abundant supply of honey. In other forms these organs, as well as the strength 
of the fragrance, are less strongly developed, and so the scale descends until in such 
plants as P. aviculare, P. littorale and the like, the fragrance, showy calyx and nectaries 
do not exist. The higher the coloring of the calyx the greater is the development of the 
1Kearney, Coult. Bot, Gaz. 16: 314. 38, Coulter. Coult. Bot. Gaz. 17: 91. 
*Meehan, Coult. Bot. Gaz 16 : 273 (erroneously published as P. acre). 4H. Miller, Fert. of Flowers, 509-516, 
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