910 RECORD OF CURRENT RESEARCHES RELATDTG TO 



b. The poles not clearly marked. 



a. The elements of tlie " plate " distributed regularly in 

 the equatorial plane of the " spindle." Most vege- 

 table cells. 

 p. The elements of the " plate " lying outside the 

 " spindle " in the equator. An unusual case in the 

 integuments of the ovule of Nothoscorodon fragrans. 

 2. The threads only slightly or imperceptibly converging to- 

 wards the poles. 

 a. The ends of the threads marked by knots. Embryo-sac 



and integument of Monotropa. 

 h. The ends of the threads not especially marked. Spirogyra. 

 II. " Nucleus-barrel " formed of a single kind of rod-like elements. 



1. The elements of the " barrel " strongly converging towards 



the poles. Integument of ovule of Nothoscorodon fragrans. 



2. The elements of the " barrel " ouly slightly or imperceptibly 



converging towards the poles. Epithelium of larva of sala- 

 mander ; cartilage of larva of batrachia. 



Conducting Tissue for the passage of Pollen-tubes.* — The 

 structure and development of the tissue which serves the special 

 purpose of conducting the pollen-tube from the stigma, through the 

 style and ovary to the micropyle of the ovule, has been made a special 

 subject of study by M. G. Capus. 



By a conducting tissue the author understands one composed of 

 cells, usually elongated, delicate, and but slightly united, the union 

 of which forms a cylinder occupying the centre of the style, or lining 

 the walls of a central stylar canal. The pollen-tube carries on a 

 parasitic existence, obtaining the nutriment necessary for its rapid 

 elongation from this conducting tissue. The development of this 

 tissue hence depends greatly on the number of pollen-tubes for which 

 it is destined to supply the nutriment, and therefore on the number 

 of ovules to be fertilized. 



This conducting tissue is always a modification and extension of 

 the epidermis, whether on the surface of the stigma itself, as a lining 

 to the stylar canal, or on the walls of the ovary or of its dissepi- 

 ment intermediate between the base of the style and the ovules. At 

 the period of impregnation the cells of this tissue are filled with a 

 dense, granular, oily and nearly opaque substance. In certain cases 

 the periblem or hypodermal tissue takes part, along with the true 

 eindermis, in the origin of the conducting tissue. Again, but 

 rarely, the conducting tissue may owe its origin to prolification, or 

 the tangential division of the epidermal cells ; more often to a similar 

 division of the hypodermal cells. The stigma, proj^erly so called, is 

 nothing but the apical termination of this conducting tissue of the 



In the ovary it is never continued below the spot from which 

 spring the lowest ovules. It is much more strongly develojjed in 

 ovaries with parietal placentation and a large number of erect ana- 



* ' Ann. Sci. Nat. (Bot.),' vii. (1879) p. 209. 



