304 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 



Haussknechtii, Boiss, a small Rafflesiaceous parasite which 

 lives upon species of Astragalus in Syria and Kurdistan. 



6. Ramification and Partition of Puncium Veyetationis. — 

 E. Warming has published an elaborate memoir on this 

 subject with eleven plates and a French resume {' Vid. Selsk. 

 Skr/ 5 R. Naturv. Math. Afd., 10 Bd.). The punctum 

 vegetationis is that region the special function of the cells 

 of which is to furnish new cells to the plant or its 

 organs. It, therefore, does not include regions the func- 

 tions of whose cells is the genesis of lateral organs, or of 

 particular tissues in the interior of organs. The terminal 

 cells (" schietelzellen"), or homologous groups of cells, are 

 therefore the pimcta vegetationis of Cryptogams, and the 

 group of apical cells discovered by Hanstein in Phanerogams 

 {" scheitelzellgruppe ") is equivalent. Defined in this sense 

 the inferior limit of the region will somewhat vary. If it is 

 held to be limited by the uppermost cell of the procambium, 

 it may be found below the highest lateral structures of the 

 stem, especially if these happen to be buds without subtend- 

 ing leaves. 



Warming's investigations on the histology of the summit 

 of the stem quite confirm those of Hanstein. In all the 

 phanerogamic plants which he has examined he found it 

 covered with a layer of dermatogen divided usually only by 

 radial partitions and sharply defined on its inner contour. 

 A single terminal cell never occurs even in Utricularia com- 

 parable with that of Cryptogams. Of the three systems 

 of meristem in the stem the dermatogen is the most con- 

 stant and the best characterised ; it is never absent even when 

 the periblem and plerome are undifiPerentiated. Generally 

 speaking, the dermatogen covers a more or less regular 

 cellular tissue. Immediately beneath it are 1-7 layers of peri- 

 blem which cover the top of the stem like a sheath, and of 

 which the cells are usually divided by radiating partitions. 

 Below these layers the stem is ordinarily composed of plerome 

 — the mother-meristem of the fibro-vascular system and the 

 pith — the cells of which are usually arranged more or less 

 vertically and regularly. Warming has not succeeded in de- 

 tecting in the different layers of periblem the cell, or group 

 of cells, which might be regarded as the punctum vegetationis of 

 each layer. But the series of cells of the plerome terminate 

 above by a group of cells segmented in all directions and 

 forming a tissue more or less irregular. This " initial group " 

 of the plerome may even consist of a small number of cells 

 arranged with great regularity or (as in the peculiar shoots 

 of Utricularia studied by Pringsheim) of a single cell, but 



