ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



Comparative Anatomy of Ambrosiacese and Senecioidese.* — The 

 examination of a large number of species belonging to these families 

 leads Herr H. Hildebrandt to the conclusion that a great many nearly 

 related species can be clearly and sharply distinguished by their 

 anatomical structure. Points of anatomical structure may therefore be 

 used for purposes of classification ; but the divisions thus established do 

 not coincide with those founded on morphological characters. Many 

 species have an altogether abnormal structure ; thus Bhynchopsidium and 

 Leyssera resemble Cruciferse. 



Anatomy of Marcgraviaceae.j — In an account of the anatomical 

 structure of this natural order, Herr O. Juel states that sclerides, either 

 isolated or associated in groups, occur commonly in the parenchymatous 

 tissue. The order is distinguished by its dimorphic branches, erect 

 fertile, and creeping sterile. The larger leaves have no stomata, while 

 the smaller leaves have stomata on both surfaces ; in the larger leaves 

 the chlorophyll-grains have a diameter of 5-9 /x; in the smaller leaves 

 they are about 20 jx long and 10 /j. broad. The ovules are very small, 

 with two integuments, of which the inner one projects far beyond the 

 other, the apex emerging almost unchanged outside the testa of the ripe 

 seed. 



(4) Structure cf Organs. 



Vegetative Organs of Brasenia peltata.^: — Mr. J. Schrenk describes 

 the structure of the vegetative organs of Brasenia peltata Pursh., a plant 

 belonging to the natural order Nymphseacese. What is described in the 

 manuals as the creeping rootstock is really a system of runners that 

 proceed from the rhizome proper. The secondary roots ai'ising at the 

 nodes are long and slender ; at the tip of each rootlet there is a sheath 

 or case which looks exactly like the finger of a glove ; it consists of a 

 single layer of elongated oblong cells, forming a distinct firm mem- 

 brane with an unbroken smooth rim. There is a central very thin 

 plerome surrounded by thin-walled endoderm cells ; the other root- 

 tissues are very loose, with large intercellular canals, and a thin epider- 

 mis. In the stem the central portion is invariably occupied by two 

 fibrovascular or mestome bundles. The two mestome bundles are 

 separated by parenchymatous tissue, and groups of intercellular canals. 



The leaf is thick, oval, and peltate, and has at most twenty principal 

 veins, converging at the centre over the petiole. The cells of the upper 

 epidermis have a peculiar structure : they are two or three times as high 

 as they are broad. The palisade-tissue underneath the epidermis is 

 composed of two or three, sometimes even four tiers of cylindrical, 

 narrow cells, with numerous air-spaces between them, and containing, on 

 their vertical walls, large chlorophyll-grains. If the epidermis of parts 

 of this plant which are in contact with water be examined, it will be 

 found to be thickly beset with hairs. The hairs are all unicellular, but 

 vary much in size and shape ; some divide into two equal or unequal 

 branches ; others again expand horizontally in the upper portion. By 

 these hairs a mucilage peculiar to Brasenia is produced. 



The author gives the results of a series of experiments with various 



* Hildebrandt, H., ' Beitr. z. vergleich. Anatomie der Ambrosiaceen u. Sene- 

 cioideen,' 52 pp. and 1 pi., Marburg, 1887. 



t Bot. Sallsk. Stockholm, Feb. 16, 18S7. See Bot. Centralbl., xxxiii. (1888) 

 p. 27. J Bull. Torrey Bot Club, xv. (1888) pp. 29-47 (2 pis.). 



1888. 2 i 



