Tis sties in Certain Monocotyledons . 35 
him was pericyclic. He describes the bursting of the endo- 
dermis in consequence of the secondary growth. The short 
account given by De Bary is practically identical with this h 
In 1884 Strasburger published an investigation of the roots 
of Dracaena reflexa , and showed that the cambium is first 
formed in the pericycle, and continues for a time to produce 
secondary tissues inside the endodermis, which thus becomes 
ruptured, but that sooner or later this activity ceases, while 
the cortical cells immediately outside the endodermis take up 
the division, and carry it on indefinitely 1 2 . The structure of 
the secondary tissues in the root is identical with that in the 
stem. 
In 1885 Morot published his important paper on the 
pericycle. He examined the secondary thickening in the 
roots of various Dracaenas. He found that it usually takes 
place in the pericycle, but may exceptionally arise in the 
cortex. This may happen when there has been very little 
activity in the pericycle, and while the endodermis is still 
continuous 3 . 
In his book on the vascular tissues Strasburger confirms 
his former statements, and adds several interesting details. 
He finds that the xylem of the first-formed secondary bundles 
abuts in each case on two xylem-groups of the primary 
cylinder, thus enclosing one of the primary phloem-groups. 
The strand of secondary phloem is connected at its lower 
end (i. e. towards the root-apex) with a primary group. At 
the places where the endodermis is ruptured the internal 
and external tissues become perfectly continuous, and 
secondary bundles extend from the pericyclic into the cortical 
zone. The roots are epinastic as regards their secondary 
thickening, which begins on the upper side, and continues to 
be more vigorous there. The cambium is pericyclic near the 
1 Comparative Anatomy, English edition, p. 622. 
2 Das Bot. Practicum, 1st edition, 1884, p. 202. This account is omitted 
from the second edition. 
3 Morot, Recherches sur le pericycle, Ann. des Sci. Nat., Bot. Ser. 6. t. xx. 
p. 247. 
