On the ‘Squamulae Intravaginales 9 of the Helobieae. 
BY 
AGNES ARBER, D.Sc., F.L.S. 
(.Keddey Fletcher-Warr Student of the University of London'). 
With five Figures in the Text. 
(i) Introduction. 
I T has long been known that certain scale-like structures, to which the 
name squamulae intravaginales , or squamulae intraaxillares , was 
given by Irmisch, are found among the leaf-bases of the Helobieae 
(Potamogetonaceae, Naiadaceae, Aponogetonaceae, Scheuchzeriaceae, 
Alismataceae, Butomaceae, Hydrocharitaceae) and of certain members 
of the related family, Araceae. The earliest published record of the exis¬ 
tence of these squamules seems to be that of Nolte (16), who, nearly 
a century ago, observed them in Stratiotes. But we owe the first compre¬ 
hensive treatment of the subject to Irmisch (10), who published a paper in 
1858 , which, though brief and unillustrated, laid the foundation of our 
knowledge of the structures in question ; he also carried his observations 
further in other papers (11, 12, 13, 14). Caspary (5), Prillieux (17), Sanio 
(18), Bornet (2), Bayley Balfour ( 1 ), Buchenau (3 and 4), T. G. Hill 
(9), Fauth (7), Harvey Gibson ( 8 ), Sergueefif (21), Cunnington ( 6 ), and 
Solereder ( 22 ) have added further information about the morphology and 
distribution of the squamules. There are many good illustrations of their 
external appearance, both in the papers just cited—especially that of 
Bornet (2)—and in Kirchner, Loew, and Schroter’s ‘ Lebensgeschichte der 
Blutenpflanzen Mitteleuropas ’ (15). Schilling (20), who has studied the 
squamules from the point of view of function, regards them as organs 
which secrete mucilage, but, according to Solereder ( 22 ), this does not hold 
good universally. 
The number of squamules found in association with each leaf may 
range in different species from two to many; each of the squamules may 
either consist of a single plate of cells, or it may be a comparatively solid 
body, in which the upper and lower epidermis are separated by several 
[Annals of Botany, Vol. XXXVII. No. CXLV. January, 1923.] 
