5 66 Hatfield. — Anatomy of the Seedling and 
Cretaceous fossil Colymbites Edwardsii. Further, an examination of the 
stem apex reveals a very definite and extensive increase of parenchymatous 
tissue, a? the result of the activity of a meristematic 4 growth zone ’ which 
cuts off pith and cortical tissues by cell-division in the tangential plane only. 
It seems likely that this method of growth has some bearing on the phe- 
nomenon of tangential extension found in older portions of the young stem. 
Finally, the structures observed strongly indicate that the phenomenon 
of 4 girdling 5 is not a new feature peculiar to the Cycadales, but is rather the 
modification of a normal leaf-supply due to two factors, (i) the telescoping 
of the axis, and (2) the activity of the growth zone referred to above. 
Material. This was found in a sandy Cycad thicket near Freemantle, 
in Western Australia, and collected by Dr. E. N. Thomas during the visit 
of the British Association to Australia in 1914. It consisted of seeds just 
beginning germination ; also of young plants of tubby habit, which had borne, 
on the average, some twenty leaves (Plate XXII, Fig. I). These plants were 
characterized by a very swollen hypocotyl and an extremely long tap-root 
(at least 60 cm. in length). There is no evidence of any decay of the tap- 
root, and it would seem unlikely that so strong and well established an organ 
should be discarded later by the plant. 1 It is possible that changes in the 
habit of these plants, induced by conditions of culture in pots, have led to the 
idea expressed by English writers that the roots of mature Cycad plants are 
wholly adventitious. This view finds support in the fact that a three-year- 
old seedling of M. Fraseri grown in England had a short and branching 
tap-root, a condition not paralleled in any specimen collected in the field. 
Plants grown from seed in England produced some ten leaves in three 
years ; the ‘tubby’ plants (Plate XXII, Fig. I) collected in Australia in 1914 
had borne about twenty leaves; it would therefore seem that they were several 
years old. But no growth stages between these and the germinating seeds 
were found. The reason for this, in the absence of continuous observations 
in the field, could not be discovered. Work of Professor Pearson, 2 which 
shows that the seedlings of W elwitschia mirabilis are probably only able to 
establish themselves in the wet seasons which alternate with several 
practically rainless years, is suggestive. Further stages in the development 
of the seedling were provided by plants grown at Bedford College from seeds 
brought home in 1914. 
Methods . The germinating embryos were embedded in paraffin and 
examined in the usual way. For the young plants, which were large and 
complicated in structure, hand-sections were at first relied upon, in combina- 
tion with series of thick slices, which were cleared with eau de Javelle and 
stained with acid fuchsin in the manner advocated by Matte 3 and used later 
1 Worsdell : Structure and Origin of the Cycadaceae. Ann. Bot., vol. xx, No. lxxviii, 1906. 
2 Pearson : Proceedings of the Royal Society. 
3 Matte : Recherches sur l’appareil libero-ligneux des Cycadees. 
