ZOOLOGY AND BOTANY, MICBOSCOPYj ETC. 431 



zonale, and states that the usual description is inaccurate which places the 

 seat of the formation of the oil between the cuticle and the inner layer of 

 the epidermis. It is first formed in the protoplasm itself, though at a 

 later stage a membrane makes its appearance between the oil-drop and the 

 protoplasm. The oil-glands on the margins of the stipules of Erodium 

 cicutarium retain permanently the earlier structure of those of Pelargonium, 

 and the same is the case also with those on the sporangia of Pteris serrulata. 

 In Ononis sjpinosa the very thin oil found in the protoplasm passes entirely 

 through the outer wall of the gland. The transverse walls of the pedicel- 

 cells of the gland are perforated by a large number of minute pores, 

 through which threads of protoplasm pass from one cell to anothei*. A 

 similar passage of oil through the outer membrane takes place in the glands 

 of Senecio viscosiis. 



Structure of Flowers of Cleome.* — By observations on two species of 

 Cleome {C. spinosa and gigantea) Herr F. Hildebrand confirms the state- 

 ment of Vochting "j" with regard to the movements of the floral organs 

 resulting from gravitation. He finds that, as the position of the flower in 

 this respect is altered, the stigmas and anthers always place themselves in 

 such positions that they are not in contact with one another ; the object 

 being apparently to promote cross-fertilization. 



Cleistogamous Flowers of Orobanchacese. | — M. L. Trabut describes 

 a peculiar kind of cleistogamous flower which he has detected in PJielippsea 

 lutea, an Orobanchaceous plant from the province of Oran. They are 

 situated below the ordinary flowers, buried in large scales, and produced 

 beneath the surface of the soil. They appear later than the ordinary 

 flowers, and produce smaller capsules, containing seeds in no way differing 

 from the ordinary ones. 



Doubling of Flowers. § — Herr F. Hildebrand points out that the 

 doubling of flowers is always a morbid phenomenon, and of no use in 

 nature ; the marking of the petals which assists insect-visitors in finding 

 the way to the nectary is usually lost. The tendency to an abnormal 

 development of the corolla (or calyx) varies greatly in different families ; 

 in many cases it is so feeble that it is exceedingly difficult in them to 

 obtain double blossoms. External influences can only act on this pre- 

 disposition in the species to a doubling of the floral organs. 



Mimetic Pollen-grains. |1 — Herr J. M. Janse records a remarkable 

 instance of mimetism in the flowers of Maxillaria Lehmanni, from Central 

 America. On the central region of the labellum is a callosity which is 

 covered by a fine yellow powder which bears an almost exact resemblance 

 to a layer of detached pollen-grains. The author suggests that they are 

 taken for pollen-grains by bees, which devour them eagerly for the large 

 quantity of starch which they contain. In moving about the labellum to 

 feed on this substance, the insect would necessarily strike against the 

 anther, and remove the poUinia with their viscid discs. The substance in 

 question appears to be an epidermal structure, consisting of tie detached 

 nearly spheroidal constituent cells of moniliform hairs. Herr Janse 

 believes that this is the first instance recorded of the occurrence of starch 

 in hairs. 



* Ber. Deutsch. Bot. Gesell., iv. (1836) pp. 329-37. 

 t See this Journal, ante, p. 266. 

 X Bull. Soc. Bot. France, viii. (1886) pp. 536-8. 



§ Pringsheim's Jahrb, f. Wlss. Bot., xvii. (1886) pp. 622-41. Cf. this Journal, ante, 

 p. 266. 



II Ber. Deutsch. Bot. Gesell, iv. (1886) pp. 277-83 (1 pi.). 



