614 SUMMARY OF CUREENT RESEARCHES RELATING TO 



grains varies between seventeen and sixty-six days, the average appearing 

 to be from thirty to forty. Attempts to influence the direction of the growth 

 of the pollen-tubes were without result. 



Nectaries.* — Di\ S. Stadler describes the structure and development of 

 the nectary in seventeen species of plants, with remarks on their mode of 

 fertilization. Melittis Melissophyllwm, Cydonia japonica, and CEnoihera 

 Lamarldana have hispid nectaries. The methods of secretion are divided 

 into four classes: — (1) Through uncuticularized tissue, as in Agave; 

 (2) Through stomata, as in Melittis; (3) Through cuticularized tissue 

 without upheaval, as in Lilium ; and (4) with upheaval of the cuticle, as in 

 Diervilla. Asclepias Cornuti has two kinds of nectary. The origin and 

 course of the fibro-vascular bundles are described in the various cases, as 

 well as the chemical reactions of the cell-contents of the nectariferous 

 tissue. 



Structure and Development of the Fruit of Anag-yris foetida.f — Sig. 

 E. Martel examined separately the development of the epidermis, and then 

 that of the fibrous zone of the pericarp. From the elements of the sub- 

 epidermal parenchyma near the fibrous bundles is formed a second solid 

 layer parallel to the fibrous stratum of the internal epiderm. The elements 

 of these two zones are differently situated, a condition which contributes 

 not a little to facilitate the dehiscence of the fruit. The author shows that 

 in the pericarp of Anagyris foetida there is no germinal zone, as stated by 

 Cave for most fruits, and he concludes his work by refuting the opinions of 

 Cave about the strata of the pericarp, and, although agreeing with Cave's 

 views in general on stems, he declines to accept those relating to the origin 

 of the layers which form them. 



p. Physiology. J 

 (X) Reproduction and Germination. 



Entrance of Pollen-tubes into the conducting Tissue.§— Dr. P. Eit- 

 tinghaus has studied the way in which pollen-tubes force their way into the 

 conducting tissue of the style. An open canal in the style occurs especially 

 in Monocotyledons. In other cases, of which CMmonantJius fragrans, 

 Camellia japonica, LytJirum virgatum, and some others are given as examples, 

 the surface of the stigma is not cuticularized, and the pollen-tubes find their 

 way with great ease between the cells. But in the great majority of cases 

 a certain degree of resistance is offered to the entrance of the pollen-tubes 

 by the more or less perfect cuticularization of the surface of the stigma. 



In these cases it is impossible to conceive that the extremity of the 

 pollen-tube has any power of mechanically breaking through the cuticle ; 

 the entrance must be effected by means of solution or absorption. The sub- 

 stance which brings about this absorption is clearly to be found in the pro- 

 toplasm of the pollen -tube, and is probably a peculiar enzyme. The passage 

 through the cuticle is effected either on a papilla or at the base of one. The 

 cuticle is absorbed by the substance contained in the pollen-tube, and an 

 intimate fusion takes place between the pollen-tube and the papilla, so that 

 the separation between them entirely disappears. 



* Stadler, S., Beitr. z. Kenntniss d. Nectarieen u. Eiologie d. Bliithen, 88 pp. 

 and 8 pis., Berlin. See H. N. Kidley in Journal of Bofany, xxv. (1887) p. 157. 



t Ann. R. Istit. Bot. Eoma, ii. (1886) pp. 51-7 (1 pi.). 



X This subdivision contains (1) Reproduction and Germination ; (2) Nutrition and 

 Growth; (3) Movement; and (4) Chemical Changes (including Respiration and 

 Fermentation). 



§ Verhandl. Naturhist. Ver. Preuss. Eheinl., xliii. (1886) pp. 105-22 (1 pi.). 



