301 
and Histogeny of Strycknos. 
this numerous class of cases the phloem-formation appeared to 
be centrifugal. Morot 1 was the first to show that in various 
Chenopodiaceae, Nyctagineae, etc., in fact throughout the 
families in question, the cambium constantly gives rise on its 
inner side to the wood of the bundles, on its outer side to 
their bast. The generative zone always passes between xylem 
and phloem^ but only has a temporary activity. In order that 
other more external bundles may be formed, it is necessary 
for new generative zones to be produced outside the first one. 
These new cambial zones may either be entirely distinct from 
their predecessors, or, as is more frequent, may have more or 
less numerous points of contact with them. In the latter case 
the original generative zone may maintain its activity in the 
intervals between the bundles, but these interfascicular cambial 
arcs become connected by bridges of meristem passing outside 
the bast, and destined to replace the generative arcs inter- 
posed between phloem and xylem. As Morot points out, it is 
the persistence in some cases of the activity of the interfascicular 
portions of the cambial ring, which led to the belief that the 
activity of the entire ring is persistent. Thus to Morot 
belongs the credit of showing that the activity of each cambial 
ring is perfectly normal throughout the whole of this 
series. 
The conclusions of Morot have been fully confirmed by 
Herail 2 , Strasburger 3 , Petersen 4 , and by the independent 
observations of one of us on Mirahilis , Bougainvillea, Cheno - 
podium , Amarantus , and Mesembryan themum . In all these 
cases, while the bulk of the secondary tissues is formed 
centrifugally, the phloem of each bundle is developed, as in 
normal cases, centripetally. 
It is to be regretted that the recent authors Gheorgieff 5 , 
1 Recherches sur le pericycle, in Ann. des Sci. Nat. Ser. vi, T. xx, 1885, p. 284. 
2 1. c. p. 247. 
3 Das botanische Practicum, 2te Auflage, 1887, p. 170. 
4 Staengel-bygningen hos Eggersia buxifolia, in Botanisk Tidsskrift, Bd. xvi, 
French resume, p. 9. 
5 Beitrag z. vergl. Anat. d. Chenopodiaceen, in Bot. Centralblatt, Bd. xxx and 
xxxi, 1887. 
