82 Sargant. — Theory of the Origin of Monocotyledons 
Miss Anderssoa (2) and M. Queva (33) have found a well- 
defined cambial zone within the bundles of some Mono- 
cotyledons, and traces of such formation in many others. 
The tuber of Corydalis solida (Jost, 28) appears to retain 
normal secondary growth in thickness. The cambium forms 
a new tuber every year within the old one, adding to the 
wood a great mass of parenchymatous elements which become 
filled with reserve food-material. The anatomy of Dicotyle- 
donous tubers has been somewhat neglected, but I believe 
this structure to be exceptional. The seedling anatomy of 
Delphinium sp. and Anemone coronaria suggests that it may be 
found in the mature tubers of these species also (pp. 54-56). 
The food supply, however, is more commonly stored in the con- 
junctive tissue and cortex ( Eranthis , Podophyllum , Cyclamen , 
and the roots of Ranunctdus Ficaria). The development of 
the cortex and conjunctive tissue inevitably isolates the 
bundles traversing the tuber. 
Early disappearance of the Primary Root . 
This character is by no means universal among Mono- 
cotyledons. In many arborescent species the primary root 
persists for a considerable time, becoming stout and well 
developed (Yucca, Palms). But the rule among bulbous and 
herbaceous species certainly is that the primary root dis- 
appears at the same time with the cotyledon. Bulbous plants 
as a rule lose their roots at the end of each growing season, 
and put out new ones at the beginning of the next. This 
habit is no doubt correlated with the direct connexion of each 
leaf with a particular root so characteristic of bulbous plants 
(cf. a quotation from Mirbel given by Mr. Henslow, 15, p. 506). 
The annual crop of roots is clearly bound up with the annual 
recurrence of a period of vegetative activity. 
Eranthis agrees in this respect with Monocotyledons. The 
primary root is replaced in the second spring by a circle of 
roots developed in a girdle surrounding the tuber (Irmisch, 24, 
Fig- !5)- 
