35a PRIMARF ARRANGEMENT OF TISSUES. 



radially and tangentially. In transverse section there appears a ring of 15-20, widely 

 separated, stronger bundles, which correspond to the central bundles of the base of the 

 leaf: surrounding the ring numerous smaller bundles are irregularly scattered; these are 

 derived from the lateral ones of the base of the leaf: in the space vi-ithin the ring are seen 

 the transverse sections of the connecting branches, vphich here also run in all directions. 

 Pr. Palinuri, calycina, and marginata resemble Pr. Auricula. Other species of Primula, as 

 Pr. sinensis, spectabilis, and elatior, have a typical Dicotyledonous ring of bundles, which 

 are very soon united laterally by intermediate bundles. On their special course, and the 

 peculiarities of many species, especially Pr. farinosa, compare Kamienski's work. 



In the Nymphseacex the system of vascular bundles of the stem (Rhizome) is usually a 

 network of anastomosing bundles difficult to disentangle, from which those for the leaves, 

 roots, and peduncles branch off at certain places, and which in stronger stems, e. g. of 

 Nuphar luteum, traverse the whole internal part of the stem, which lies within a sharply 

 limited cortex, even to its very centre. It may be seen from Unger's figure' how 

 chaotic this structure is. Nageli {I.e. 121) tried to explain the matter by the investiga- 

 tion of weaker rhizomes of Nymphaea alba. I reproduce his description as follows. Inter- 

 nodes shortened. Leaves arranged spirally. The transverse section shows between pith 

 and cortex a circle of separate bundles, which is divided usually into three, rarely into four 

 groups, which can be recognised with the naked eye. The three groups are of unequal 

 width : they vary continually throughout the length of the stem, and are related to the 

 arrangement of the leaves. The bundles of the circle are often connected with one 

 another, so that, when seen in surface view, they appear as a network. -The middle of 

 the pith is traversed by a central bundle, which throws off now and then a branch to 

 the net-work. 



From the base of the leaf five bundles enter the stem : three of these lie rather higher 

 and form the true leaf-trace. Their lateral bundles separate widely from one another, 

 and weave themselves in with the net-like circle at two almost diametrically opposite 

 points, so that the trace is about 180° wide. The median bundle also loses itself usually 

 at once in the net. But sometimes it passes inwards through the pith, after forming 

 some anastomoses with other bundles, and unites with the central bundle. In one stem 

 it was the 8th and 13th, in another the ist, 6th, nth, i8th, and 32nd leaves, the median 

 bundles of which passed to the centre, while those of all the other leaves remained in the 

 outer network. In the first example the 8th and 13th, in the second the ist, 6th, nth, 

 and 32nd leaves were on the upper side of the procumbent stem, the 18th on its lower 

 side. 



An independent growth of the central bundle at its apex was not observed : Nageli 

 therefore considers it as a sympodium of median bundles. 



I found in weak rhizomes of Nuphar pumilum that the transverse section resembled 

 that described in the case of Nymphsea : an irregular ring of 8-1 2 bundles, and a central, 

 often vei-y eccentric, and frequently branched bundle being seen : the latter is in rare cases 

 entirely absent from the section. The bundles of the ring form a net with elongated 

 meshes, the main meshes being limited by the bundles of the leaf-trace, between which 

 smaller bundles, usually pushed back rather further into the pith, form an irregular net- 

 work. The leaf-trace consists of three bundles, and is about 120° wide, the median 

 bundle forks in the node into two shanks diverging at an obtuse angle : each of these in 

 its descending course is united with the lateral bundle of its own side. I never saw the 

 median bundle curve to the middle line of the stem, but rather I here saw only a bundle, 

 which ran irregularly from side to side, and here and there gave off a lateral branch and 

 anastomosed with the peripheral net. An independent ending of this bundle beneath the 

 growing-point was not to be found. Besides this I have examined but few preparations, 

 and wished in the above remarks only to point to N. pumilum as an object well suited for 

 the elucidation of the structure of the stem in the NymphxaceEe. 



' Anatomie und Physiologie, p. 235. 



