1915] BLODGETT—LEMNA FROND 385 
develop but slowly, as compared with the bud anterior to it, 
which represents the daughter frond; thus when the latter is as 
shown in fig. 10, the axillary bud is only as shown in fig. 2, or in 
figs. 6 and ro. 
The next stage marks the beginning of the upper wall of the 
inclosing pouch by which the bud will be protected until large 
enough to project beyond the pouch margin. This first appears 
as a sharp projection just anterior to the bud of the daughter frond, 
as shown in fig. 6. At first the bud and the protective ridge are 
both in the median region of the young frond, and nearly opposite 
the root rudiment; but with the continued growth of all parts, 
the space available for vertical enlargement becomes insufficient 
and there is a lateral shifting of the dorsal structures. The bud 
itself becomes divided into two groups of cells, each a potential 
growing point. The development of the pouch wall is shifted from 
the position of a covering which is directed posteriorly over the 
bud, to that of an outgrowth which is directed obliquely backward 
from either side of the original position. 
A further change follows this shifting of the bud. The over- 
growing wall is displaced along with the inclosed bud, and thus 
there are formed two pouches at the base of the frond. The pouch 
walls, which are first recognized as a slight ridge anterior to the 
bud rudiment, extend around this as a flattened ring having its 
insertion along the side of the elongating base or stem of the frond 
and laterally on the widening frond. At the ends there is but 
little projecting growth of this ridge, but from the portion just 
above and below the inclosed bud a considerable development 
takes place. The pouch walls merge into the body of the frond 
completely at their insertion. 
A vascular connection remains between the two buds after 
they are separated by the upward growth of the supporting tissue, 
as is shown in fig. 9. No distinctly vascular elements are develope 
at this stage, but the elongated cells here shown are their rudiments. 
This figure also indicates the unequal development of the opposite 
buds. In Lemna trisulca there is less difference in development 
than in most species, but the general sequence of stages is 
similar. 
