12 BOTANICAL GAZETTE [JANUAR 
but the cells have thicker walls and a rounded outline, indicating 
that in that region the period of activity of the cells is past. The 
stem of this plant does not show good examples of cambium, nor do 
A. scoparius or A. jurcatus show the feature, even in the leaf-sheath. 
A further example is shown in fig. 12, which represents a bundle 
from the stem of Erianthus Ravennae 1-2™™ above the level of inser- 
tion of the leaf-sheath. A similar appearance is presented by the 
bundles of the sheath. The leaf-trace bundles of Zizania frequently 
show a large amount of their phlcem radially arranged, in spite of 
the fact that dicotyledoncus aquatics generally show a marked 
reduction of their cambium. The examples so far cited include 
only the more striking instances of cambium found in the family. 
More or less plain evidences of cambium have also been observed 
in the following species: (1) In both stem and leaf-sheath; Coix 
lachryma, Panicum crus-galli, Avena sterilis, Lolium italicum, L. 
perenne. (2) In stem; Tripsacum dactyloides, Miscanthus sinensis, 
Pennisetum longistylum, Panicum sanguinale, Leersia oryzoides, 
Sporobolus Wrightii, Calamagrostis canadensis, Arundo Donax, Avena 
sativa, Briza maxima, Panicularia americana, Bromus inermis, 
Triticum sativum. The occurrence of a cambium in the region 
just above the nodes in grasses recalls the well-known power which 
members of this family possess of bending upward at these regions 
if the stem is by any means laid horizontally. In this connection 
it is of interest to note that PLowMAN (11) has found only traces of 
cambium in the sedges, and in line with this, the stems of sedges 
are unable to right themselves if bent over into a horizontal position. 
Miss ANDERSSON (3) has reported the occurrence of a more or less 
plain cambial zone in the young plants of representatives of many 
monocotyledonous families. She calls attention to the similarity 
between the bundles in the seedling of Lilium and those in Ranun- 
culus. The only grass referred to is Zea, in which the mature _ 
bundles often show a radial arrangement of the cells between xylem 
and phloem, as is illustrated by the well-known figure in SACHS’ 
Text-book. From the occurrence of cambium in the tuberous stems 
of Gloriosa, QuEvA (7) has already concluded that the mono- 
cotyledons are derived from dicotyledons. In the case of the 
grasses it would seem that the cambium possessed by the ancestors 
i 
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