1902] BRIEFER ARTICLES 307 
Atkinson) has reported them on potato stems. Devaux’ describes 
oedemata on potato tubers kept saturated; they naturally appeared 
where the resistance to their growth was least—at the lenticels. 
_ Tubeuf* has reported what is doubtless the same result of excessive 
moisture on trees. They may also occur on roots in water.’ Von 
“Mohl® describes such structures formed under the influence of mois- 
_ ture from the lenticels and cortical parenchyma of Salix viminalis 
es. 
In plants whose normal habitat is wet, there has been an oppor- 
‘unity for natural selection to develop and utilize the excessive growth 
_ of the cells under the influence of water; and the utilization has been 
it several ways. The most common of these adaptations is aeren- 
_ chyma.** The oedemata of the lenticels of stems serve to connect 
: perfectly the normal aerenchyma of water plants with the oedemata of 
_ keaves. It is a matter for individual judgment when it should be 
regarded as in the nature of a disease, and when as a normal structure. 
Even in water plants (Goebel e¢ a/.) its formation depends on the 
moisture and can be artificially regulated. It is not unusual for struc- 
fares pathological in one plant to be normal in another. But no 
‘Stucture can be regarded as normal on a plant where it occurs too — 
aay for it to be subject to development by natural selection. a 
. ‘Seems entirely justified in deriving the excessively light and 
= Porous tissue of of Aeschynomene and.other plants in water from aeren- 
Be Ih these this tissue serves as a float. It is formed in the leaf cae 
mithus (Neptunia) natans, the petiole of the water hyacinth 
sa the stem of Nesaea,’? and the root of Sesbania.* The — = 
ea des lenticelles chez la pomme de terre et quelques : 
“pan Bs 38: 48-50, 1891. | 
a "Ty Se 
— ‘on he Vey a Le siesta Waker (Aerenchym) an Holger 
a mete aturw. Zeits. 405-414. 1898; Rev. in Bot. Centralb. 77: 369. a 
oe HL v., Oedema in roots of Salix nigra. ,BoT. GAZ. ee 1807. 
i eae 259-332. Flora, 1832. oe 
appa K, H., Ueber das Ae erenchyma, ein dem Kork holes Gene 
ieee Jahrb. Wiss. Bot. 20: 526-574. 1889. 
: dag et Schtideriagew i = 
es oo ff. Fig. 69 is abnormal — {oed 
Sedna) “eens : 
mI On the floating tissue of Nesaea vertcillate. ‘Bull Tor. ~~ : 
a t. and Wac ce, H., On the floating roots of Sebonia eae 
sad I: 307-314. 1888. 
