ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 55 



With regard to their function, the author does not admit that lenti- 

 cels exist primarily for the general interchange of gases ; for they are 

 often absent or inadequate ; the plant often has other porous regions 

 which serve for aeration ; and the opening and closing of the lenticels 

 is not due to the needs of aeration. They are to he regarded rather as 

 organs of transpiration for the regulation of the internal moisture of 

 the plant. 



Relation between Lenticels and Adventitious Roots in Solanum 

 Dulcamara.* — J. A. Terras states that the adventitious roots do not, in 

 this species, arise below or grow out through lenticels, as is apparently 

 the case in the majority of plants. As the first formation of the root 

 precedes the appearance of phellogenetic divisions, it is entirely inde- 

 pendent of the formation of lenticels. The protuberances on the surface 

 of the stem are not lenticels, but result from the formation of a mass of 

 secondary tissue which originates in the reaction of the phellogen to the 

 pressure set up by the elongating root below it. The lenticels appear 

 only after the protuberances are fully formed. 



Development of Hairs.f — W. Hirsch accepts Weiss's classification 

 of hairs, according to their mode of growth, as basipetal, acropetal, and 

 intercalary; but points out that even in hairs of the third type, the hair 

 does not undergo continual division from the base to the apex ; on the 

 contrary, the intercalary divisions are always confined to definite zones, 

 and the intercalary is almost always accompanied by either a basipetal 

 or an acropetal mode of growth. The mode of growth of hairs is not 

 dependent on the systematic position of a species, though within each 

 species it is constant. 



Structure of Hyacinth Roots.:}: — Ida A. Keller finds that secondary 

 roots developed from hyacinth bulbs after the bulb had partially decayed 

 and had then been restored to a growing condition by cleaning, differed 

 in no essential respect from the original adventitious roots, but usually 

 displayed a greater development of vascular tissue. 



Formation of Tubercles in Plants.§ — N. Bernard agrees with Stahl 

 in his conclusion that an endophytic mycorhiza is probably necessary 

 to the germination of the seeds of certain plants which constitute a 

 biological group displaying a symbiosis altogether analogous to that of 

 lichens. Infection by spores of the symbiotic fungus has a tendency 

 to produce tubercles ; and in plants which belong to this symbiotic 

 group there is tendency to the production of tubercles at a very early 

 period, as in the prothallia of the Ophioglossaceae and of species of 

 Lycopodium. The presence of an endophytic fungus appears to be a 

 very wide-spread cause of tuberculisation in plants. 



Influence of the Removal of the Flowers on the Root-tubercles 

 of the Leguminosse.|| — Prof. 0. Mattirolo has experimented on the 

 effect produced on the root-tubercles of Leguminosas (chiefly Vicia 



* Trans. Bot. Soc. Edinburgh, xxi. (1000) pp. 341-53 (2 pis.). 

 t Beitr. z. wissensck. Bot. (Fuufstiick), iv. (1000) p. 1. See Bot. Centralbl., 

 lxxxiv. (1900) p. 166. 



t Proc. Acad. Nat. Set. Philadelphia, 1900, pp. 438-40 (1 pi.). 



§ Comptes Kendus, exxxi. (1900) pp. 626-9. Ci. this Journal, 1900, p. 707. 



|| Malpighia, xiii. (1900) pp. 382-421 (1 pi.). 



