DR. W. R. McNAB ON WELWITSCHIA. 509 
flower (fig. 10). After this the stamens elongate rapidly, and soon attain their full 
length. 
The male flower is thus constructed of four series of opposite and decussate parts— 
two outer lateral parts of the perianth, two inner (anterior and posterior), two lateral 
primordial stamens, and two carpels (anterior and posterior). The growth of the flower 
goes on without interruption till after the formation of the carpels, when an arrest 
of growth takes place, and it is only by slow degrees that the central part or end 
of the axis elongates to form a conical projection. The early stage at which the carpels 
surround the central part prevents the pollen grains reaching the punctum vegetationis ; 
and in none of the flowers observed were pollen grains seen inside the cavity, neither 
was there any appearance of an embryo-sac, nor, indeed, any differentiation of the tissue 
in the end of the axis. 
Development of the Female Flower. 
In its earliest stages the female flower appears as a minute papilla, with a rounded 
apex and a compressed basal portion (fig. 11). The formation of the two lateral parts 
of the perianth of the female flower takes place above the basal portion, where there is a 
constriction. The basal part is quite thin and has a broad base, which expands as the 
flower grows, and is perfectly free and unattached to the bract in the axil of which the 
flower is produced. This stage is represented in fig. 12. In the next stage, as seen in 
fig. 13, we observe the basal portion and the two shoulders now very much enlarged, 
while above them the axis is nearly cylindrical for a short distance, the whole ter- 
minating in a rounded punctum vegetationis. The parts of the perianth now elongate 
. rapidly ; and above, a ring is formed surrounding the punctum vegetationis. The central 
part is now the naked nucleus, while the ring surrounding it is the ovular integument. 
In this flower the two inner parts of the perianth, the two primordial stamens, and the 
two carpels are not developed, the space between the integuments probably indicating 
that certain structures are wanting. In fig. 14 a young flower, with the two lobes of the 
perianth, is represented, and also the naked nucleus and integument. The nucleus 
projeets above the, other parts; and on looking at the same flower from above, the 
relation of the parts is distinctly seen (fig. 15). The ring-like structure contrasts strongly 
with the two carpels in the male flower, and seems to indicate conclusively that the 
disputed part of the female flower is not carpellary. In the next stage (fig. 16) the 
perianth has increased in size, and now overtops the other parts, while the integument 
has not yet covered the nucleus. In fig. l7 the enlarging perianth is still seen, the 
nucleus is also indicated, and the integument may be observed rising round it. Figs. 18 
and 19 show still more advanced flowers : the perianth is closing ; and now the embryo-sac 
is visible in the nucleus. 
Conclusion. 
The difference in the male and female flowers is remarkable. In one dimerous 
symmetry prevails, while in the female flower the three inner whorls are wanting. We 
thus have the outer lateral parts of the perianth of the male corresponding to the two 
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