670 Chronicles of Science. [ Oct., 
border of which at a later period forms the teeth of the sheaths, and 
that, on this account, their resemblance to the foliar organs is rendered 
doubtful. The siliceous covering is considered as a secretion of the 
part of the epidermal cells which is in contact with the air. It is an 
inorganic secretion outside the cells, and resembling in some respects 
the waxy matter deposited on the surface of the leaves and fruits, Full 
details are given of the structure of the stomata; their position being 
limited to the parts of the epidermis which cover a parenchyma filled 
with chlorophyll. The vascular system of Equisetums consists of a 
cylinder of distinct and very regular bundles of annular or spiral vessels. 
Regular lacune also occur in the inside of these bundles, formed by 
the absorption of the more internal of the vessels. The development 
of spores resembles that of the pollen-grains, and the spiral filaments 
surrounding the spores are formed from the outer membrane of the 
spore itself. These spores when germinating produce, as in ferns, a 
small green irregularly-lobed frond or prothallus, called by M. Duval- 
Jouve Sporophyme. On the prothallus are produced Antheridia filled 
with spermatozoids or antherozoids, and Archegonia containing each 
a germ-cell or embryonary-cell, destined after fecundation to produce 
the fructiferous frond. The prothalli are usually unisexual. The 
expulsion of the antherozoids and their application to the Archegonia 
are favoured by humidity. The following species are described : 
1. Hquisetum maximum, Lam. 2. EH. sylvaticum, L. 3. EH. pratense, 
Ehrh. 4. FE. arvense, L. 5. H. littorale, Kuhl. 6. H. limosum, L. 
7. E. palustre, L. 8. EH. ramosissimum, Dest. 9. EH. variegatum, Schl. 
10. EH. trachyodon, Al. Bra. 11. E. hyemale, L. 
IV. CHEMISTRY. 
(Including the Proceedings of the Chemical Society.) 
Tux short space we can devote to the Chronicles of Science in this 
number, obliges us to condense into the smallest bulk the little we 
have to record of the progress of Chemistry. 
Following our ordinary arrangement we may first draw attention 
to some experiments with oxygen, which, although made some time ago, 
have but recently become known to English chemists. Dr. Meissner,* 
of Gottingen, has devoted himself to a thorough investigation of the 
ozone and antozone question; and in the course of his experiments 
has obtained some curious results. The most singular, perhaps, is 
the discovery that antozone possesses a remarkable attraction for 
water, which it takes up in the shape of vapour forming a mist or 
cloud. This the author supposes to explain many meteorological 
phenomena. In the course of the experiments he also satisfied him- 
self that ozone and antozone are produced from ordinary oxygen in 
* «Untersuchungen tiber den Sauerstoff.’ Hanover, 1863. 
