ASCIDIA IN GASTERIA AND AGAVE. 131 
Puel and Saint-Pierre * also observed an ascidium in 
this form. The fourth leaf was transformed into a sack 
with a small opening at the tip through which the stem ex- 
tended. The fifth leaf was normal while the sixth also had 
the margins partly fused. The veins of the leaf forming 
the main ascidium are described as of equal size. 
Itis now quite impossible to draw any conclusions con- 
cerning the ascidia described as diphyllous in Convallaria 
and Polygonatum, but the normal arrangement of the 
leaves in these forms and the condition found in the other 
Monocotyledons in which ascidia have been found suggests 
that possibly these anomalies are monophyllous in origin. 
Leaves showing a more or less complete longitudinal di- 
vision into two component parts are among the commonly 
described foliar anomalies. There are two processes by 
which such structures might arise: — by the fusion of two 
adjacent primordia or by the longitudinal division of 
one already formed. The numerous cases which have been 
described have been referred, by implication at least, 
to one of these categories. Paxf and Kleint have sug- 
gested criteria for determing the probable method of de- 
velopment of any individual case, butsince the necessary data 
are wanting a correct interpretation of most of the pub- 
lished descriptions is quite impossible. But for our present 
purpose it is sufficient to note that either the production 
of two primordia in the region where only one normally 
occurs or the broadening of the single primordium by 
division increases the total width of the meristematic 
region from which a foliar organ is developing. If this 
region comes to extend entirely around the axis, tubiform 
ascidia such as those described in this paper may result. 
A broadening of the leaf accompanied by longitudinal 
* Puel and Saint-Pierre. Bull. Soc. Bot. Fr. 1: 62-63. 1854. 
+ Pax, F. Allg. Morph. Pfl. 92. 1890. 
} Klein, J. Jahrb. Wiss. Bot. 243 425-498. pl. 13-18. 1892. 
