144 de Fraine .— The Seedling Structure of certain Cactaceae. 
globular hypocotyl, which terminates in a short, slender root (Fig. io). 
The marked increase in succulence in the hypocotyl is correlated with 
a decrease in the size of the cotyledons, which in some species 
of the genus show extreme reduction. In the seedlings in 
which the cotyledons attain their maximum development, they 
consist of small pointed structures with an almost circular 
base of insertion ; while, on the other hand, the almost com¬ 
plete suppression of the pointed apex in Echinopsis multiplex 
results in the diminution of the seed-leaves to such an extent 
that they are merely represented by two papillae. In every 
case, however, no matter how reduced the cotyledons may 
be, a difference in size between those of any one plant can 
always be observed. 
Fig. io. 
Echinopsis 
Lagermannii. 
x 2. 
The Tubercle. 
The tubercles with their tufts of spines, which are so characteristic 
a feature in so many of the Cactaceae, have received attention from several 
observers with a view to the elucidation of their morphology; and 
Darbishire 1 very briefly summarizes the principal views which have been 
put forward. The appearance of the cotyledonary buds at the extreme 
base of the seed-leaves has been already noted above for some species of 
Cevens, Pilocereus , and Phyllocactus , e. g. C. tortuosus , C. Jamacaru, Pilocereus 
exerens , P. albispinus , and Phyllocactus Hookeri , and in the following species 
of Echinopsis precisely similar buds appear: E. oxygona , E. Eyriesii , and 
E. Zuccarinii. In other species, e. g. E. multiplex , E. tubiflora , and E. 
Lagermannii, these cotyledonary buds attain comparatively large dimensions, 
and where their development is most complete they closely resemble the 
tubercles which arise on the epicotyl. In some species of Mamillaria , to 
be described later, the cotyledonary bud is absolutely indistinguishable from 
the epicotyledonary tubercle, and can only be identified by its subsequent 
fusion with the seed-leaf. A well developed cotyledonary bud consists 
of a mass of tissue composed of large, parenchymatous cells, and throughout 
its length runs a single vascular bundle ; at the apex of the bud is a cushion 
of tissue on which the ends of the spines are inserted, and a cork cambium 
separates this cushion from the underlying tissues (Fig. n). When 
a comparison is made between the anatomy of a ‘ cotyledonary bud ’ and 
that of the tubercle of an adult plant, such as is described by Darbishire, 2 
there is seen to be a very close resemblance in structural details between 
the two. From these considerations it is concluded that the ‘ cotyledonary 
buds ’ of the seedling are morphologically identical with the tubercles of 
the mature plant. 
1 Darbishire, O. : loc. cit. 
2 Loc. cit. 
