ADULT ANATOMY OF WELWITSCHIA MIRABILIS. 333 
the three portions had a common base. The two main lobes were widely separated 
and were each surrounded by the well-developed inner ridge. 
Cases in which one lobe or bud is more strongly developed than the other are fairly 
common. 
In conclusion, it will be obvious from this description of the development in 
seedlings of Welwitschia that the epicotyledonary stem is extremely reduced in . 
this plant, and that practically the whole tuberous mass, commonly known in the 
adult plant as a stem, is morphologically the swollen hypocotyl which bore in rapid 
succession the two cotyledons and the two plumular leaves. The stem apex gives 
rise only to these two leaves and is suppressed early in the life of the seedling. It is 
finally in most cases even buried by the growth of the cotyledonary buds. 
The only portion of the plant which can be regarded as the epicotyledonary stem is 
that which. undergoes intercalary growth above and below the leaf-bases In the early 
stages the leaves originate at practically the same level as the cotyledons; it is only 
later that they become widely separated by further growth, which begins between the 
margins of the cotyledons as a small projection and finally develops into the outer ridge. 
But it must be noted that this ridge does not elevate the leaf-bases in a manner which 
can be compared with the separation of two nodes by the ordinary elongation of an 
internode. The ridge is a quite independent structure and has from the beginning a 
special vascular supply. It appears very doubtful whether either it, or the inner ridge, 
which originates later by intercalary growth on the inner side of the groove, can really 
be regarded as normal epicotyledonary stem. These ridges are rather of the nature of 
specialised placental outgrowths on either side of the leaf-base. 
In any case the extent of this growth-region is extremely small in comparison with 
the large swollen hypocotyl, which may also grow considerably in length (E marks 
the level of the feeder in fig. 45); the many peculiarities of the vascular structure and 
transition are probably to a large extent attributable to this remarkable elongation of 
the hypocotyl. ; ai 
The plant is really an “adult seedling”; and there are few forms with which it can 
strictly be compared. It presents some points in common with seedlings f Araucaria 
Bidwillii. At that stage in the growth of a seedling of Araucaria Bidwillii at which the 
cotyledons wither, the plant “ is capable of resisting drought, and may be sent to Europe 
It has been suggested that the first stage of 
season, while the resting stage coincides 
living in a climate in which the period 
further in its 
without losing the power of germination. 
germination may correspond with a short rainy 
with the period of drought” *. Welwitschia, ; 
of drought is indefinitely prolonged, appears to have got very little 
development than has such a seedling! def 
It will be seen later that in its anatomy, especially in the transition r : 
other points of still more striking resemblance to various species of Areucaria t 
egion, it has 
Araucaria Bidwillii) and C (Araucaria imbricata). 
* 
Seward and Ford, 1906, p. 331; see figs. 13, B ( blance between Welwitschia and 
* Attention has been called by Prof. Pearson to another striking resem 
Araucaria (Pearson, 1909, p. 370). 
