1915] BLODGETT—LEMNA FROND 389 
fused to adjacent parts (as in III of the text figure), as is the case 
on the posterior surface of the bud scale in the runner bud shown 
at I. The vertical thickening of the tissues at the insertion of the 
bud would tend to split the meristem group of cells so that a pair 
of lateral buds would finally result, as in the Lemna structure. 
The protective inner scale of the bud, which is represented in 
diagram III as bent backward under the overlying pouch wall, in 
the Lemna frond shown at IV, is fused with the posterior margin 
of the foliar tissues of the frond, and laterally to the side of the 
stem. This pouch wall arises as a ring about the base of the bud 
which it will finally inclose, and is therefore homologous with the 
development of the scale leaf about the stem tip of a bulb, or a bud 
of the Erythronium type. Under the adjustment to space and 
pressure, the ring is flattened to a narrow eclipse, and is divided by 
the same conditions as those which divide the bud within. 
In the region immediately below the stem apex in bulbs, and 
the corresponding point in Lemna, the root initials are developed; 
this region is indicated in the diagrams by cross-hatching, adjacent 
to bin I, II, II]. In Lemna only one root is regularly developed, 
but in Spirodela several are formed. The activity of the adjacent 
apical meristem evidently continues for a considerable period, 
allowing for the successive formation and development of new 
fronds within the same parent pouch. The old fronds are released 
by the separation of the cells close to the insertion of the stem upon 
the parent tissues, apparently by the breaking down of the middle 
lamella of a band transverse to the stem. The stump left in such 
a case is seen at sin fig. 2. By the enlargement of the axillary bud 
this stump will be obliterated before the new frond is far advanced. 
Conclusions 
The Lemna frond is a propagative structure consisting of a 
terminal leaf; a bud inclosed by a flattened bud scale, the base of 
which is fused to the base of the leaf and laterally to the stem; and 
an apical region from which new fronds are developed. Two buds 
are formed through the splitting of a single bud rudiment by 
vertical pressure during early stages of growth. The frond meets 
the conditions of a floating habitat in which the tension of the 
