212 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
«y. General. 
Myrmecophilous Plants.^ — In the concluding portion of his work 
on' this subject, Prof. F. Delpino enumerates as many as 3030 species, 
distributed through 292 genera, with extra-floral nectaries or other 
contrivances for inviting the visits of ants. The natural orders in which 
the greatest number of myrmecophilous species occur are Mimoseac (663), 
Euphobiacese (482), and Bignoniacese (342). The prevalence of the 
phenomena in any district is nearly proportional to the average tempera- 
ture; the central- American region produces the largest number (653). 
The author believes that both ants and myrmecophilous plants came 
into existence in the Cretaceous period. 
Injury to Vegetation from Gases.j — Herren L. Just and H. Heine 
describe the injury done to vegetation by various gases, the most injurious 
being sulphurous acid, which, when taken into the tissues, is oxidized 
into sulphuric acid, which gradually destroys the protoplasm, causing 
yellowing of the leaves and final death of the plant. Apple and pear 
trees, the grape-vine, and conifers, are especially sensitive to its 
attacks. 
Botanical Work of Lacustrine Stations. J — Prof. F. Ludwig calls 
the attention of botanists to the scheme pi oposed by Zacharias for the 
investigation of lakes. The distribution of aquatic plants, the actual 
conditions of life, the relations between fauna and flora, e. g. in con- 
nection with fertilization, all demand investigation, for which the 
establishment of lake-side stations is indispensable. “ When the 
‘ systematic ’ survey of a country is roughly completed, then the ‘ bio- 
logical ’ investigation begins,” and it is time that this was undertaken 
in earnest for the lakes. 
B. CRYPTOGAMIA. 
Cryptogamia Vascularia. 
Antherozoids of Marsileaceae and Equisetace8e.§— Continuing his 
researches on the structure and development of the antherozoids of 
Cryptogams, M. L. Guignard now describes those of Pilularia and 
Equisetim. 
The antherozoids of Pilularia he finds to be formed on the same 
general plan as those of the Characeae, Muscineae, and Filices; the 
nucleus, which has taken up a lateral position in the mother-cell, and 
gives birth to the spiral body, partially absorbs the granular and 
starchy protoplasm ; the rest of the protoplasm forms a vesicle, con- 
taining particles of starch, which remains attached to the internal face 
of the posterior portion of the body, and becomes detached only during 
the rotation of the antherozoid. The general aspect of the antherozoid 
closely resembles that of Sphagnum, differing chiefly in the number of 
cilia. The cilia are not attached, as has been stated, to the two first 
* Funzione mirmecofila del regno vegetale,’ pte. 3, Bologna, 1889, 35 pp. See 
Bot. Centralbl , xl. (1889) p. 387. Cf. this Journal. 1888, p. 998. 
t Landwirthsch. Versuchsstat., xxxvi. (1889). See Bot. Centralbl., xl. (1889) 
p. 296. X Biol. Centralbl., ix. (1889) pp. 414-6. 
§ Bull. Soc. Bot. France, xxxvi. (1889) pp. 378-83. Cf. this Journal, 1889, p. 552. 
