Scott and Mas ten. — The Structure of Trigonocarpus. 105 
parenchymatous cells which probably represent but a portion of a more 
extensive tissue 1 . 
The detailed structure of the seeds of the Cycads has been 
recently described by Miss Stopes 2 . The ‘ outer flesh ’ or sarco- 
testa, which is universally present, is composed of parenchyma with 
numerous gum canals and tannin sacs and is bounded externally by an 
epidermis of radially elongated cells. The sarcotesta is traversed by 
a series of vascular bundles which spring from the central supply bundle 
entering at the base of the seed. In position these bundles lie opposite 
to the longitudinal ridges of the underlying * stone ’ or sclerotesta as 
has been described above in Trigonocarpus. In the Cycads the number 
of sarcotestal bundles always corresponds exactly with the number of 
ridges, so that in Macrozamia spiralis where the stone is provided with 
twelve well-marked ribs there are also twelve bundles, while the bilateral 
seed of a Cycas which possesses only two ridges has only two bundles, 
although each bundle contains two vascular strands in some species. As 
described above, in Trigonocarpus it is probable that the sarcotestal 
bundles occur opposite to certain of the longitudinal ridges only, not to all. 
Returning to the Cycads the individual sarcotestal bundles are de- 
scribed as collateral with mesarch xylem. In some forms, such as Cycas 
circinalis , the bundles are of a simple type with external phloem and 
internal xylem provided with a considerable development of transfusion - 
tracheides, the whole bundle being surrounded by a sheath composed 
of peculiar cells provided with reticulated lignified thickenings 3 . 
In some other forms the sarcotestal strands are more complex in 
structure although their position remains the same. In Cycas media 
each strand consists of two collateral bundles with their phloems directed 
towards one another, so that the outer bundle of the two has, of course, 
reversed orientation. The xylem of each bundle is mesarch, and the 
inner one of the two possesses a considerable development of transfusion 
elements 4 . In Cycas revoluta the bundles run in pairs through the outer 
flesh. 
In yet other species the structure becomes still more complex, for 
in Cycas Beddomii the whole strand, consisting of two bundles embedded 
in fine conjunctive tissue containing many transfusion elements, is sur- 
rounded by a well-differentiated sheath composed of the peculiar cells 
mentioned above in Cycas circinalis 5 . 
As far as can be judged from the transverse sections of imperfectly 
preserved sarcotestal bundles around the body of the seed such as that 
shown in PI. XIV, Fig. a8, Trigonocarpus Parkinsoni conforms to the 
simplest of these types, that of Cycas circinalis , but owing to the imperfect 
1 Oliver (’ 04 ) (2), p. 98. 2 Stopes (’ 04 ). 3 Stopes (’ 04 ), p. 440. 
4 Stopes (’ 04 ), p. 442. 5 Stopes (’ 04 ), p. 445, Fig. 8. 
