de Fraine .— The Seedling Structure of certain Cactaceae . 167 
Anemone coronaria , l a cotyledonary tube is present, but the transition is 
of the ordinary Ranunculaceous type in which there is a diarch root and 
no hint of tetrarchy. Thus it is seen that the development of a cotyledonary 
tube may or may not give rise, even in seedlings of the same family, to the 
Anemarrhena- type of vascular rearrangement; while this same type may 
occur, as has been shown above, in seedlings in which there is not the 
slightest sign of cotyledonary fusion. 
It cannot be considered that the resemblance of Opuntia , for example, 
to Anemarrhena is the result of a close genetic relation between the two; 
nor can it be conceded that it is due to a response of two unrelated forms 
to similar conditions ; hence we cannot but conclude that the resemblance 
is accidental. This being so, then it is quite possible that the similarity 
of Eranthis and Podophyllum to Anemarrhena is also accidental, more 
especially as the other two related seedlings, Delphinium and Anemone , 
do not diverge from the normal Ranalian type, though they might naturally 
be expected to do so, on analogy with Eranthis. 
The theoretical importance of the anatomical resemblance of Eranthis 
to Anemarrhena has already been denied on other grounds by Tansley. 2 
Miss Sargant, in her paper on the ‘ Reconstruction of a Race of Primitive 
Angiosperms ’, 3 has put forward many reasons for the probability of a 
dicotyledonous Proangiosperm ; she concludes that the monocotyledonous 
condition arose by a fusion of the cotyledons in adaptation to a geophilous 
habit, the fusion taking place on account of the need for strict economy 
which must be observed by the seedling. But, as has been already pointed 
out, the evidence on which the ‘ fusion ; hypothesis was based has been 
considerably weakened by the discovery of the Anemarrhena type in 
seedlings of such a specialized order as the Cactaceae ; moreover, the 
economizing of time and material may have taken place in at least two 
other ways without necessitating any theory of fusion. It may have 
occurred :— 
1. By the gradual suppression of one cotyledon of an ancestral 
pair, or, 
2. By the assumption of different functions by the two cotyledons. 
The first of these views, the ‘ suppression ’ hypothesis, was supported by 
Prof. Henslow, 4 and Miss Sargant 5 has summarized the most important 
evidence given by him in support of his views. 
Charles and Francis Darwin 6 have shown that dicotyledonous plants 
1 Sargant, E.: loc. cit. 
2 Tansley, A. G.: Reduction in Descent. New Phyt., i, p. 132. 
3 Loc. cit. 
4 Henslow, G. : A Theoretical Origin of Endogens from Exogens by Adaptation to an Aquatic 
Habit. Linn. Soc. Journ., xxix, 1892. 
5 Sargant, E.: Reconstruction of a Race of Primitive Angiosperms. Ann. Bot., xxii, 1908, 
P- 1 75 - 
6 Darwin, C. and F.: Power of Movement in Plants, 1880, p. 94. 
