366 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
leaves. The strong development of latex-tubes favours the supposition 
that these structures perform the function of retaining water in the 
tissues. In Sonchus the latex-tubes occur, not, as in other genera, by 
the side of the phloem-bundles, but in the cortex and pith of the stem. 
This genus again differs from the others in the absence of sclerenchy- 
matous elements. Spherocrystals are formed in many species by treat- 
ment with alcohol, or I on drying; they usually consist of inulin, 
sometimes of calcium phosphate. Crystals of calcium oxalate are widely 
distributed. The author finds that, as a general rule, morphological 
differences are correlated with differences in histological structure. 
Anatomy of Maize.* * * § — Dr. J. W. Harshberger gives a brief descrip- 
tion of the anatomy of Zea Mays , together with a detailed account of its 
origin, distribution, cultivation, and uses. 
Leaves of Nymphaeaceae.f — Dr. F. Brand points out that our 
European w r ater-lilies have three distinct kinds of leaf, an aquatic 
(submerged), a floating, and an aerial form. The primordial leaves of 
the seedling are aquatic, long, narrow, folded and shortly stalked, and 
with a thin epiderm. In Nujpliar luteum the greater number of the leaves 
are aquatic, the production of floating leaves being limited to the warmest 
portion of the year ; the minimum [temperature for their formation 
appears to be about 10° B. (12*5° C.). The aquatic leaves have a much 
longer length of life than the floating, and are the most important in 
their biological functions. A well-developed floating leaf has, however, 
about three and a half times the weight of the best developed aquatic 
leaf. The aerial leaves, which are formed especially in shallow water, 
resemble the floating leaves, except in the absence of a palisade layer. 
In Nymphsea alba the aquatic leaves have a shorter term of life and play 
a less important part in the biology of the plant. Aerial leaves are more 
frequent than in Nuphar. 
Leaf of Butomacese.J — M. C. Sauvageau describes the structure of 
the leaf of the four genera belonging to this natural order of aquatic 
Monocotyledons : — Lymnocharis, Hydrocleis, TenagocTiaris, and Butomus. 
The last-named genus differs from the other three in having equitant 
leaves ; in the complete absence of laticiferous vessels, and of an apical 
opening to the leal ; and in the presence of spiral fibres in the vicinity of 
the vascular bundles. 
Fall of Leaves.§ — Herr B. v. Ihering adduces several instances of 
trees belonging to the tropical and subtropical zone of Brazil which lose 
their leaves when growing in moist, but are evergreen in dry situations. 
He gives his opinion that the evolution of species with deciduous leaves 
took place only in the Tertiary period. 
Stipules of Euonymus.|j — Herr L. Linsbauer has studied the struc- 
ture and development of the minute deciduous stipules which occur in 
several species of Euonymus , and probably in all the Celastraceae. 
* Contrib. Bot. Labor. Univ. Pennsylvania, i. (1893) pp. 75-202 (4 pis.), t 
t SB. Bot. Yer. Miinchen, Jan. 8, 1894. See Bot. Centralbl., Ivii. (1834) p. 168. 
X Ann. Sci. Nat., xvii. (1893) pp. 295-326 (9 figs.). Cf. this Journal, 1892, p. 63. 
§ Atti Congr. Bot. Internaz. Genova, 1892 (1893) pp. 247-59. See Bot. Centralbl., 
ivii. (1893) p. 50. 
|1 Oesterr. Bot. Zeitschr., xliii. (1893) pp. 301-5, 340-6 (1 pi.). 
