de Fraine .— The Seedling Structure of certain Cactaceae. 145 
Owing to the greatly depressed stem apex, which often results in the 
appearance of a short apparent cotyledonary tube, the tubercles may seem 
in some cases to be situated on the cotyledon itself, instead of in its axil; 
but longitudinal sections through the seedlings indicate that the tubercles 
are really auxiliary structures and are not outgrowths from the cotyledon. 
With regard to the morphological nature of the tubercle and spines 
it has been stated by Goebel 1 that in many Cacteae, ‘ the spines are trans¬ 
formed leaves which arise upon very much reduced lateral shoots standing 
in the axils of the leaves.’ In another connexion he remarks 2 that in many 
Cacti, ‘ the thorns are here usually arranged in tufts on very short shoots,’ 
Fig. 11. Echinopsis Lagermannii. Group of thorns on the cotyledonary tubercle. 
L. S. x 109. 
and that 4 the thorns are transformed leaves’. He further observes 3 that in 
many Cactaceae, especially in the Mamillarieae, 4 the axillary shoot 
44 grows up upon ” its subtending leaf—that is to say, the common base of 
the two is elongated.’ Darbishire, 4 however, 4 can see in the mature tubercle 
only the highly developed leaf-base. The spines together represent the 
leaf-blade, the leaf-stalk being absent.’ 
The development of tubercles in the axils of the cotyledons appears to 
support Goebel’s view that the tubercles represent short shoots, but it is 
desired to carry out further investigation along experimental lines before 
expressing any very definite opinion as to their morphological nature. 
The tubercles in the Echinopsis group show a very well marked rise 
in importance when compared with the cotyledons ; increase in size of the 
1 Goebel, K.: Organography of Plants, Oxford, 1905, Part I, p. 168. 
2 Loc. cit.. Part II, p. 429. 3 Loc. cit., Part II, p. 436. 
4 Loc. cit. 
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