1904] SARGANT: EVOLUTION OF MONOCOTYLEDONS 337 
appears, and then the cambial layer within each bundle, for no 
development of secondary elements is needed. 
The structure of some living geophytes illustrates this process. 
In the first and second year tubers of Eranthis* and Arum,” for 
example, we find the slender leaf traces isolated among the 
abundant parenchymatous tissue which is packed with starch. 
The Cyclamen tuber is formed in a similar way. 
Though this method of tuber formation is quite common, it 
is not universal. Jost’s researches on Corydalis solida* show the 
tuber to be formed in this species by the activity of a normal 
cambium which adds a mass of parenchymatous elements to 
xylem and phloem alike. The reserve food is stored in the 
tissue thus produced. Each year sees a fresh tuber formed 
Within that of last year, which it destroys. My own observa- 
tions on first-year seedlings of Anemone coronaria and Delphinium 
nudicaule show that their tubers are formed in a similar way. 
The tissues —chiefly parenchymatous— which thicken them 
are added by a normal cambium. I have not examined older 
seedlings or mature plants. 
Podophyllum offers the best example with which I am 
acquainted of a dicotyledon which, according to the present 
hypothesis, may be considered as arrested on the way to become 
amonocotyledon. A full account of the seedling and mature 
plant of P. peltatum is given in Mr. Holm’s interesting memoir,”* 
to which I must refer readers who wish for fuller detail. Owing 
to his kindness in sending me seeds, I have been able to examine 
the first-year seedling anatomically. 
As in Evanthus hiemalis, the blades only of the cotyledons 
are distinct. Their petioles are united into a long tube, the base 
of which is beneath the surface of the soil. The hypocotyled- 
onary axis is vertical and very short, but not swollen into a 
tuber. Its tissues are packed with starch. It is terminated 
*SarGANT, E,, /. c., pp. 57-61, and fi. 6. 
“Scott and SaRGantT. The development of ‘Arum maculatum from the seed. 
Annals of Botany 12: 404-413. 1898 
Jost, Die Erneuerungsweise von Corydalis solida Sm, Bot. Zeit. 48:257- 1890. 
*HoLM, TH., Podophylium peltatum. BOT. GAZ. 27:419. 1899- 
