ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 63 



tracheids, without cell-contents. The vascular bundle of the leaf, which 

 is collateral throughout, has an exarch structure in the lamina, the proto- 

 xylern lying next the phloem. The phloem contains true sieve-tubes 

 with transverse sieve-plates, on both sides of which callus is formed. 

 The stele of the root has in all parts a monarch structure, the differentia- 

 tion of the xylem beginning with the development of a single tracheid, 

 which lies exactly opposite the protophloem. 



The observations of the authors tend to confirm the view of the 

 affinity of Isoetcs with Lycopodium rather than with the Filices. 



Anatomy of the Hymenophyllaceae.* — A study of the structure of 

 several species of Hymcnophyllum and Trichomanes leads L. A. Boodle 

 to the following conclusions. 



The stem is in all species monostelic, and one leaf-trace passes off 

 to each leaf; the stele contains no pith. In the stem of Hymenophyllum 

 the phloem forms a ring round the xylem. In Trichomanes the stele 

 exhibits several different types of structure, viz. : — (1) a ring of xylem 

 surrounding the parenchyme which contains the protoxylem (T. reni- 

 forme) ; (2) a solid mass of xylem with internal protoxylems accom- 

 panied by only scanty parenchyme (T. radicans, &c.) ; (3) the sub- 

 collateral type (T. trichoideum) ; (4) the collateral type (T. muscoides) ; 



(5) only one tracheid, or none at all, and no phloem (T. labiatum) : 



(6) a solid mass of xylem with scattered indefinite protoxylem (T. 

 spicatum) ; (7) a solid mass of xylem with distinct peripheral proto- 

 xylem (T. scandens). 



The leaves of all Hymenophyllaceae are destitute of stomates, as 

 well as of intercellular spaces, even though they are several cells in 

 thickness, as in T. reniforme. 



Stem of Angiopteris.j — Miss E. F. Shove has made a study of the 

 anatomical structure of the stem of Angiopteris evecta. The vascular 

 strands are arranged in a series of inverted funnel-shaped zones ; the 

 leaf-trace bundles arise from superficial vascular tissue alone ; the steles 

 of the second zone do not share in the formation of the foliar strands. 

 The centrifugal growth of the phloem is contrary to that described for 

 most other Ferns. In the apical region of the stem the presence of 

 several initial cells was satisfactorily demonstrated. The stem is 

 apparently destitute of aerial roots. 



Algae. 



Cell-division in Fresh-water Algae.*— Prof. R. Chodat states that 

 in some filamentous fresh- water algae (Baphidium, Kirclmeriella, Scene- 

 desmus), transverse septation frequently takes place ; the second cell- 

 division is often at right angles to the first ; two of the daughter-cells 

 being then at the poles of the mother-cell, the other two lateral. A 

 similar mode of septation takes place in Volvox. 



New Genera of Floridese.§ — Among algae from our southern coasts, 

 E. A. L. Batters finds types of no less than three new genera of 

 Florideae, viz. : — 



* Ann. of Bot., xiv. (1900) pp. 455-96 (3 pis.), 

 t Tom. cit., pp. 497-525 (2 pie.). 

 I Arch. Sci. Phys. et Nat., ix. (1900) pp. 491-2. 

 § Journ. Bot., xxxviii. (1900) pp. 369-79 (1 pi.). 



