922 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



result of the conducting bundles in the primary veins of the leaf, and 

 also frequently those of the leaf-stalky having an eccentric structure. 

 The layer of phloem which surrounds the xylem is much more 

 strongly developed on the under than on the upper side. 



3. The history of development of the collateral bundles in ferns 

 is completed in the same way as in flowering plants. The differen- 

 tiation of the xylem and phloem begins (in transverse section) at two 

 opposite points of the cambium-bundle, and advances centripetally in 

 relation to the action of the bundle. 



4. A general parallel may be drawn between the dorsiventral 

 structure of the mesophyll and the collateral-eccentric development of 

 its vascular bundles. The more conspicuous the dorsiventrality of the 

 assimilating system, the more striking is the collateral-eccentric 

 structure of its conducting bundles, 



i 5. It results from these observations that, certainly in the case of 

 ferns, most probably in that of flowering plants, the collateral struc- 

 ture of the vascular bimdle, and its origin in the flatly expanded 

 lamina of the leaf, is a primary anatomical fact. The anatomico- 

 physiological dorsiventrality of the lamina is thus represented also in 

 the structure of its conducting bundles. 



Phyllocladus.* — T. Geyler has fully investigated the structure of 

 Phyllocladus trichomanoides. The scale-leaves on the primary axis 

 dry up and fall off early. They are arranged spirally, as are conse- 

 quently the cladodia formed in their axils. There is, however, a 

 considerable space in which the axillary cladodia are wanting, fol- 

 lowed by one in which they are crowded and almost verticillate. The 

 cladodia themselves form a system of secondary and tertiary branches, 

 and so on, in the axils of corresponding scale-leaves. The branches 

 of the weaker primary cladodia are arranged in a single plane, while 

 with the more vigorous cladodia this is the case only in the lower 

 part ; in the upper part the arrangement is spiral, that part of the 

 cladodium having a round section. In the next year, such a clado- 

 dium developes at first sterile leaves, followed by a number of almost 

 verticillate secondary cladodia. 



In seedlings, after the first pair of bi-nerved cotyledons, acicular 

 leaves were produced, and in the axils of some of these, cladodia vary- 

 ing greatly in their distance from one another. In shoots of the third 

 year these acicular leaves gave place to others more resembling the 

 scale-leaves of older plants. The leaves borne on the first formed 

 cladodia differ in form from those produced subsequently. After the 

 third year three-lobed cladodia are formed ; and later some are even 

 many-lobed, resembling a pinnate leaf. 



The author's description of the fibrovascular bundles does not 

 differ from that of previous observers. 



Hibernating Prothallia of Equisetum.t — In view of the probable 

 genetic connection of vascular cryptogams with the Muscineae, and 



* Aljbandl. Seuckenberg. Ge3., xii. (1880) pp. 11-17 (2 pis.). See Bot. Cen- 

 tralbl., vi. (1881) p. 313. 



t Oesterr. Bot. Zeitsehr., xxxi. (1881) jip. 245-8. 



