Thiselton-Dyer . — Morphological Notes . 557 
of illustrations drawn from all parts of the vegetable kingdom 
accumulated by Lord Avebury in his work on ‘Seedlings’ 
will show that in an immense proportion of cases, cotyledons 
are foliaceous. Nor can they be regarded as suctorial in 
cases such as are present in the Leguminosae, where they have 
become mere reservoirs of accumulated food- material destined 
for the future nutriment of the young plant. 
I confess that all the evidence seems to me to point to the 
fact that cotyledons, whether suctorial, store-organs or folia- 
ceous, must still be regarded as foliar organs. Lord Avebury 
(Vol. I, pp. 9, 10) cites the opinion of Klebs, who observes 
that ‘ on the whole the forms of cotyledons are much simpler 
than those of leaves, and . . . that while in some cases perhaps, 
like the first leaves, they retain the form which characterized 
the species in bygone ages, we may rather, as a more generally 
applicable explanation, apply to them the suggestion of 
Goebel with reference to stipules, and regard them as simplified 
by arrest.’ Lord Avebury adds that another suggestion has 
been that cotyledons are ‘ a survival of the universal foliage 
of deciduous trees in olden geological days, ere time had 
differentiated them into their present varied forms.’ 
That cotyledons preserve a more ancient and primitive type 
of foliage is in accordance with the general facts of embryology. 
The cotyledons have their own battle to fight, but it is not 
that of the adult plant, and adaptations suitable for the more 
strenuous struggle would be superfluous in the simpler conflict. 
This consideration is strengthened by the case reproduced in 
Fig 30 of a young seedling of Libocedrus macrolepis . In this 
after a time there is a complete change in the form and dis- 
position of the foliar organs. The primitive leaves, which are 
not very different to the cotyledons with which they are 
serially continuous, no doubt represent a generalized and un- 
modified type of foliage. 
An analogous but distinguishable phenomenon is described 
by Asa Gray in the case of the common pea (Botanical Text- 
book, p. 19) : — 
‘The plumule . . . usually rises as a stout stem of several 
