120 BOTANICAL GAZETTE [SEPTEMBER 
is an important condition for the existence of shade flora. In such plants, 
in order that the daily products of photosynthesis may compensate the respira- 
tion of darkness, there is required at 18° C. an average illumination of little 
more than o.o1 light; and in order that growth may be maintained, in the case 
of Oxalis, a minimum daily illumination of 0.25 light for somewhat more than an 
hour. In sun plants an equilibrium between respiration and photosynthesis 
is reached at about 0.025 light—Gro. D. FULLER. 
Prothallia from sex organs of Polypodium.—SrTe1L’ has reported that “in 
an old culture of Polypodium irioides the sterile cells of a large number of 
antheridia and archegonia became vegetative like ordinary prothallial cells.’ 
No case of regeneration from the sex organs of a pteridophyte has been reported 
previously. The cap cell and ring cells of the antheridia produced prothallial 
filaments and secondary antheridia; while the cells of neck and venter of the 
archegonia also prodpted Poreoe ta and antheridia, but in no case secondary 
archegonia. Th n this way reached maturity, developing 
actively motile sperms. ‘It was impossible to state under what cultural con- 
ditions the cells of the sex organs regenerated, but it is suggested that the 
peculiar behavior was . result of unfavorable conditions which appeared in 
the old culture-——J. M 
Oxalophytes over limestone.—Recent studies by SaLisBuRY and TANSLEY” 
have shown that Quercus sessiliflora, regarded as a decided oxalophyte, occurs 
in the regions under consideration over limestones. Analyses, however, prove 
that leaching has so reduced the lime content of the surface soils that they are 
often really acid in their reactions, and hence the oak seedlings and the accom- 
panying calcifugous herbaceous vegetation really develop in a non-calcareous 
or even in an acid soil. This adds another to the rapidly accumulating array 
of facts indicating how dangerous it is to assume that calcareous rocks always 
give rise to calcareous soils.—Gro. D. FULLER. 
Stock-poisoning plants—LAwrENCE™ has published an account of the 
principal stock-poisoning plants of Oregon for the use of ‘‘the Oregon farmer or 
stockman.”’ The statement is made that ‘‘the annual toll of the poisonous 
plants in Oregon is surprisingly heavy.” It is of interest to botanists to note 
that the principal poisonous plants of Oregon are Delphinium (6 spp-), 
Zygadenus (2 ni Cicuta ° spp.), Lupinus (x sp.), Astragalus (1 sp.), and 
Pteridium (1 sp.)—J. M. C 
9Stem, W. N., The development of prothallia and antheridia from the sex 
organs of Polypodium irioides. Bull. Torr. Bot. Club 48:271-277. figs. 4. 1921- 
3 ury, E. J., and Tanstey, A. G., The Durmast oak-woods (Quercela 
sessiliflorae) of the Silurian and Malvernian strata near Malvern. Jour. Ecol. 9:19-38- 
pl. I.. 1921. 
™ LAWRENCE, W. E., The principal stock-poisoning plants of Oregon. Oregon 
Agric. Coll. Exper. Sta. Bull. 187. pp. 42. pls. 2. figs. 10. 1922 
