SYSTEMATIC BOTANY. 489 



that in the pre-formed embryoblastic vesicles, the apex of the pollen-tube 

 only produces a primary embryonal cell ; and that at a subsequent period 

 long after the pollen-tube has been destroyed, this grows into the embryo- 

 blaston in the same manner as the pollen-tube does at first from the 

 pollen-cell. In accordance with this hypothesis, the simplest expression of 

 the impregnation of the Gymnosperms would be found in their embryo 

 not being formed in the pollen-tube itself, but in the apex of one of its 

 secondary cells, the development of which does not commence until a long 

 period after it had lost its parent-cell. 



PALIVLE. The eighth part of V. Martius's large work on the Palms has 

 appeared, (Monach. 1845, fol.,) containing the conclusion of the text, a 

 Memoir upon Fossil Palms, by Unger, and the commencement of the mor- 

 phology of the family from the pen of Martius himself. The text includes 

 the completion of Phce.nix and the Cocoineee. The contents of the morpho- 

 logical section, in which at present the stem and the formation of the leaves 

 are treated of, are more histological and physiological than systematic. The 

 fibrous root formed during germination is soon succeeded by the formation 

 of the rhizome from an axillary system of branches of the base of the stem 

 ( 23) with new radicles, which may protrude through any part of the cor- 

 tical layer of the rhizome (24) whilst the branches of a higher order arise 

 only from the axillary buds of the rudiments of the leaves of the rhizome, 

 and therefore, like the stem, they only possess the vascular bundles of the 

 leaves, and not unfrequently grow into turiones. After the earlier radicles 

 are dead, the older palm-stem rests upon adventitious roots, which arise late- 

 rally from the lower part of the stem, generally in the vicinity of the scars 

 of leaves; which contradicts Schleiden's explanation of this phenomenon. 

 (Grundziig. i, Ausg. 2, p. 122.) The structure of the stem is very fully 

 described. The results agree essentially with those of Mohl : the remark 

 that the vascular bundles do not always return to the bark on the same side 

 of the stem as that upon which the corresponding leaf is situated, but on 

 the opposite side, so that they traverse the entire stem in an oblique direc- 

 tion, is new. The vascular tissue of the root appears to be different from 

 that of the stem. The morphology of the leaf is not yet completed, and 

 partly differs, in the genesis, from Mirbel. It appears clear, from the plates, 

 that the segments are really formed by the subdivision of a simple lamina. 

 The course of the lateral vascular bundles indicates the segments even when 

 the lamina is simple. 



TYPHACEJS. Schnitzlein has described this group. (Die Natiirl. Familie 

 der Typhaceen mit besonderer Kiicksicht auf die Deutschen Arten. Nord- 

 lingen, 1845, iv, p. 28.) The morphological considerations are based upon 

 an accurate investigation of the structure of Typha angustifolia and Spar- 

 ganium natans. The author considers the Typhacese as more closely allied to 

 the Cyperacea? than to the Aroideaj, which is, however, at variance with the 



