ZOOLOGY AND BOTANY, MICROSCOPY, ET C. 4.~> 



teristic, however, is the variation in the size, form, etc., of the tubercles. 

 An interesting biological difference between the wild and cultivated 

 forms of I), prehensilis is the presence in the former of a thick bush i if 

 spiny rhizomes at the summit of each tubercle. These rhizomes grow 

 round the tubercle below the soil and sometimes protrude beyond the 

 surface. Such rhizomes do not occur in the cultivated forms. 



Studies on Roots.* — H. von Alten has studied the root structure of 

 various herbaceous and woody Dicotyledons, and finds that in the former 

 the old roots are successively replaced by younger ones, but that the 

 differences in structure found in old and young roots are due to 

 difference in age, and not, as stated by Tschirch and others, to difference 

 of function. Both nourishing and attaching roots have the same 

 structure at the same age. On the other hand, the roots of woody 

 Dicotyledons show a difference in structure consequent upon difference 

 in function. The lower part of the main root and its attached roots are 

 at first similar to those of herbaceous plants, but later on two distinct 

 kinds of roots are to be noticed, viz., attaching roots and nourishing 

 roots. The author considers that herbaceous plants have typically 

 dimorphic roots, while heterorhizy is characteristic of woody plants. 

 The present paper concludes with some general remarks upon the 

 structure of the central cylinder in the two kinds of roots, the number 

 of protoxylems, and the formation of hypodermis, cork, and endodermis. 



Studies in JCginetia.f — S. Kusano publishes an account of his studies 

 of the embryology of JEginetia indica, and the results obtained tend to 

 throw light upon our present knowledge of phanerogamic parasites. JEiji- 

 netia shows transitional states between autophytic and advanced parasitic 

 life, and the chief results of the author's observations are as follows :— 

 The seed will only germinate under the stimulus of the host-root, the 

 stimulus being due to some substance excreted and diffused throughout 

 the soil. After being kept dry for two years the seed loses its power of 

 germination. The host-plant may be a Vascular Cryptogam, Gymno- 

 sperm or Angiosperm, and the stimulant excreted is probably common 

 to all the higher plants. Although all roots can stimulate the germina- 

 tion, tlje seedlings will only develop upon certain natural hosts. The 

 first stage of germination is the transformation of the epidermal cells at 

 the radical end of the embryo into hair-tendrils, and no further develop- 

 ment takes place until attachment to the host is effected. When this is 

 accomplished, spherical tubercles arise in the neighbourhood of the 

 tendrils, owing to some stimulant provided by the host. Some tubercles 

 are differentiated into a primary haustorium, and the remainder into 

 root and shoot. 



Reproductive. 



Gametophytes and Fertilisation in Juniperus.| — A. M. Ottley 

 has studied the development of Junvperus communis and J. virginiana 

 with the following results. The staminate cones have many sporophylls 

 with microsporangia on their under surface. The female cones have 



* Bot. Zeit.,lxvii. (1909) pp. 175-98 (2 pis. and 8 figs.), 

 t Bot. CmtralbL, xxiv. (1909) pp. 286-300 (2 pis.). 

 \ Bot. Gaz., xlviii. (1909) pp. 31-46 (4 pis.). 



