148 de Fraine .— The Seedling Structure of certain Cactaceae . 
One cotyledon in Series 3 is also similar to E. Lagermannii , but in the 
second cotyledon there are three equal bundles present; two of these fuse 
and later form one half of the ‘ double ’ bundle, while the second half is 
produced by the fusion-product of the third cotyledonary bundle and the 
tubercle-trace. 
A study of the various methods of formation of the two bundles 
always found towards the upper part of the hypocotyl in the species of 
Echinopsis examined, leads to the conclusion that the behaviour of the 
cotyledon-bundle depends almost entirely upon the stage of development 
of the vascular supply of the tubercle; where the latter is absent or is 
poorly differentiated, the former dominates the transition ; on the other 
hand, where it is well developed it shares equally with the seed-leaf-trace, 
and may even play the more important part. 
A further detail in connexion with E. multiplex assumes interest when 
compared with the Mamillarias to be described later. In this species the 
epicotylar strands contribute a fair share to the root-structure, while in the 
other species of Echinopsis examined, the bundles, even when fairly well 
developed, play no part in the formation of the root. 
The Hypocotyl. 
The globular hypocotyl in Echinopsis is remarkable for the enormous 
development of its large parenchymatous cells; the vascular tissue appears 
but of slight dimensions when compared with the non-vascular tissue. 
The curious cortical lobing of the hypocotylar base, which was men¬ 
tioned above as occasionally occurring in some members of the Cereus 
group, is an almost constant feature of Echinopsis species. Towards the 
base of the hypocotyl the outer layers of the cortex grow downwards for 
a short distance, very closely enveloping the upper part of the root. The 
growth may take place in a complete circle around the axis, so that 
a transverse section, at a level towards the base of the region of downward 
growth, shows a remarkable zoned structure, the primary root having the 
appearance usually associated with an adventitious root embedded in the 
cortex of a rhizome. More usually, however, it occurs only at two or 
more places, so that at a lower level the cortex is lobed. This growth 
rarely attains an equal depth all round the axis, hence it often appears, in 
transverse section, as though an outer layer of cortex were being gradually 
peeled off. 
The upper part of the root, as in most of the other genera, just below 
the region of exfoliation of the cortex, is closely invested with long root- 
hairs ; below this, again, there is a more or less well marked superficial 
cork formation. 
