ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 53 



cutinized cells began to break down. This fact, interpreted in the light 

 of the foregoing experiments, induces the author to regard Meyer as in- 

 correct in stating that the cntinization of the root is a safeguard against 

 loss of food materials ; on the contrary, it appears to be a protection 

 against loss of water under conditions of physiological dryness of soil. 



Root-cap of the Leguminosae.* — E. Tiegs has studied the origin of 

 the root-cap of Vicia villosa, Pisum sativum, and Trifolium repens, and 

 finds that it arises through growth of the dermatogen and of the cells 

 adjoining the suspensor. These " limiting cells," as they are termed by 

 the author, divide so as to give rise to root-cap above and plerome and 

 periblem below, and they are regarded by many authors as the transverse 

 meristem characteristic of the majority of roots, but this view appears to 

 be incorrect. The origin and mode of growth of the root-cap in the 

 Leguminosag is extremely like that found in the Cruciferee, and in Pisum 

 it resembles that of Helianthus. The central portion of the root-cap, 

 i.e. the columella, arises from the daughter-cells of the " limiting cells," 

 and its breadth depends upon their number. It is highly probable that 

 the periblem and plerome arise from their own initial cells, for such 

 cells can be found in the main root of Pisum sativum and Trifolium 

 repens and in the lateral roots of Vicia villosa. 



Secondary Growth in Palms.f — J. C. Schoute publishes the results 

 of his comprehensive investigations as to the growth in thickness of 

 palms. The author's method consisted in a comparison of cross- 

 sections, made at equal heights above the soil, of specimens of different 

 ages. The first section of the paper deals with the presence of secondary 

 thickening, and in the 96 species examined 31 showed an undoubted 

 growth in thickness, in 27 it was absent, and doubtful in the remainder. 

 The second section deals with the anatomical details of secondary 

 growth : the results agree with those of Eichler and others. Secondary 

 growth takes place in the outer part of the central cylinder, and the 

 chief zone of growth is the sclerenchyma associated with the vascular 

 bundles. This growth is due to division of the outer radially elongated 

 selerenchyma-cells, while the inner cells thicken early and take no part 

 in secondary growth. This explains the cessation of growth in thickness 

 in older parts of growing stems. In a few cases, in which a protoxylem 

 was present, there was secondary growth in the xylem parenchyma. 

 The growth in the sclerenchymatous tissues causes changes in the 

 other tissues. The epidermal and cortical cells become tangentially 

 flattened, and soon afterwards the epidermis splits and cork and lenticels 

 are formed. The medullary parenchyma has many schizogenous spaces, 

 and the cells are much elongated. In many palms, e.g. Pinanga 

 coronata, secondary growth only proceeds until that part of the stem 

 is covered with leaves ; in other species it continues longer. The 

 author terms secondary thickening like that of the palms, " diffuse " 

 thickening, as opposed to the normal cambial thickening. 



* Jahrb. wiss. Bot., lii. (1913) pp. 622-47 (1 pi. and 14 figs.). 

 t Zeitschr. Bot., v. (1913) pp. 392-4. See also Ann. Jard. Bot. Buitenzorg, xi. 

 (1912) pp. 1-209. 



