88 BOTANICAL GAZETTE [JULY 
features. The stele presents 6 ‘“‘stages’’ of development, differing in the num- 
ber and arrangement of the bundles; while 5 kinds of endodermis are recognized. 
An interesting series of facts is recorded in reference to the “adaptation of 
some leaves for a double life,’ and also their “adaptation for different levels 
of water.’’ Another adaptation explained is the ‘arrangements in stems and 
leaves for the purpose of resisting the impetus of the waves and the current of 
water,” 6 kinds of stem structure being recognized. All of these anatomical 
variations are not merely observed, but are arranged in evolutionary sequence. 
Numerous hybrids are recognized by means of. the new characters used, as 
well as by sterile pollen grains and “deformed stigmata.” In - ating hybrids 
are very sterile, but sometimes sterility was found to occur also in “genuine 
ies.” The 138 species, 37 of which are described as new, and the 62 
ized hybrids are grouped in 26 sections. When it is remembered that 
pipcheate” has been credited heretofore with approximately 65 species, this 
increase to 200 species and hybrids indicates that it is a much more complex 
assemblage of forms than has been supposed. In general, the species and 
hybrids are described in great detail, not only including the pct aaiany taxo- 
nomic characters, but also their anatomy and “biology.’’ In short, the 
monograph treats of the taxonomy, morphology, anatomy, and ecology of 
Potamogeton.—J. M. C. 
Pennsylvania trees.—One of the best of the recent tree manuals issued by 
various states comes from Pennsylvania.” It consists of two parts, the first 
devoted to an elementary discussion of the principles of forestry, the second 
consisting of an illustrated manual of the trees of the state. Among the topics 
treated in an interesting manner are the character of forest stands, their 
natural and artificial reproduction, the form and structure of trees, including 
a large number of photographic studies of bark, types and structure of twigs, 
buds, leaves, flowers, and fruit, and the structure of the wood. In the second 
part the keys and descriptions appear to be adequate and the illustrations 
decidedly superior to those usually seen. An entire page is devoted to each 
species, and the drawings include, in addition to the usual leaves and fruit, 
careful sketches of the Bowers, buds, and leaf scars. The term “tree” is so 
: beoetly | interpreted as to it le - such _ woody rise as Rhus — Acer 
EBrruorpo 
| Pe bal rey 
~ 
pe ae 1 lee 245 *  e ly iustrated jou al ta ae 
Z colored plates and popular descriptions of Sedum di 
— Catasetum Scurra, Chionodoxa Luciliae gigantea, Agave age ek : 
Tillandsia aa and Echeveria australis. ett MC. 
, Cymophyllus Fraseri, Rhus hirta sepanesee ae — : 
