224 NOTICES OF BOOKS. 
constructed of more than one row of cellules, contrary to the generic 
character. There is, indeed, a most close affinity in structure between 
S. Gmelini and C. lacerata, and they cannot be separated generically 
without violence,” É 
From the very nature of the ease, Dr. Harvey has not been able to 
add much to our knowledge of the curious matters which have lately oc- 
cupied the investigations of Thuret, Derbés, and Solier; but the work is 
not altogether without information on these points. The antheridia, 
for instance, are figured im Polysiphonia ramentacea. Many useful | 
practical observations are interspersed amongst the commentaries; as à 
specimen we extract a passage under the article Polysiphonia, which 
may be useful to some of our readers. “In studying the species, it is 
absolutely necessary to make cross sections of the stem, in order to be 
able to count the number of primary tubes in each internode; for 
though the exact number is not of specific importance in the Polysipho- 
nous species, where we find the same species varying in different spe- 
cimens from twelve to twenty tubes, yet it is essential to determine 
whether there be only four or more than four; and, generally speaking, 
the species with fewest tubes are most constant to their number. A 
little practice will enable the student to make the necessary sections, 
with the help of a small-bladed knife, and a botanical simple micro- 
scope, for which may be substituted a watch-maker’s eye-glass. A small 
piece of a stem or branch, say a quarter of an inch long, is firmly held 
by the finger of the left hand upon a slip of glass under the lens, while 
thin slices—the thinner the better—are cut from it. These wheel-like 
slices, floated in a drop of water, may then be placed under the com- 
pound microscope and examined. In slicing dried specimens, it is best 
to eut the stem if possible before it be moistened, as a thinner and 
cleaner eut can then be made, aud the risk avoided of the too rapid 
decomposition from the fresh water. When the cells refuse to re- 
sume their proper shape on remoistening, a drop of muriatic acid will 
frequently, but not always, expand them.” 
Such remarks are very valuable to the young student; and as every- 
thing esoterie is happily vanishing from science, it is no shame to be 
able to say with sincerity and intelligence, even in such matters, “ vi- 
ginibus puerisque canto.” E 
