ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 833 



results at which he has arrived * respecting the speciality in the 

 structure of anthers which causes their dehiscence in different ways 

 in different cases. 



Vegetative Organs of XJrtica dioica-t— Dr. A. Gravis takes the 

 anatomy of the vegetative organs of the common nettle as a basis for 

 a general and comparative study of the Urticaceae. The minute 

 structure of the stem, root, and leaf is worked out and exemplified 

 under all modifications attendant ui^on age and biological conditions, 

 and the importance of recognizing these conditions and states is 

 insisted on. This treatise would be an excellent vade-mecum and 

 guide for any student who wished to undertake serious work in 

 vegetable histology. The style of exposition is as clear as are the 

 illustrative figures.^ 



Anatomy of Peduncles compared with that of the Primary Axes 

 and of Petioles.§ — M. E. Laborie is led to conclude from numerous 

 researches that the organization of the floral axes differs very 

 frequently from that of other portions of the plant. 



Of the differences observable, the ones that may be termed essential 

 are always found when the structure of the peduncles is not identical 

 with that of the stem ; the others, accessory in some sort, vary with 

 the species. The former affect the constitution itself of the tissues or 

 systems of tissue occurring in all the axes, and their relative im- 

 portance. The latter are due to either the absence in the peduncle 

 of some tissue which exists in the stem, or the presence of some 

 elements which the stem does not possess. Thus as regards 



A. Essential Characters. — There is generally observable in the 

 pedimcles (1) a great development of the bark (Hibiscus syriacus, 

 AntirrJdnum majus, &c.) ; (2) An organization of fibrovascular bundles, 

 characterized (a) in its external portion by a frequent augmentation 

 of the diameter of the fibres, independently of their number, which 

 may be diminished (Cornus sanguinea, Gatalpa bignonioides) ; or 

 increased (Lathyrus sylvestris) ; {b) in its interior portion, by a very 

 marked reduction of the number and size of the large vessels (Dolichos 

 sinensis, Vitis vinifera, &c.). (3) Lastly the small size of the pith 

 (^Aquilegia vulgaris, Graiiola officinalis, Quercus pedunculata, &c.). 



B. Accessory Characters. — Various tissues, constant elements of 

 the stem, do not always recur in the peduncles. For instance, tbe 

 disappearance in it is noticed of cork (Lonicera alpigena, Bibes mal- 

 vaceum), of chlorophyll-colls (Arisfolochia sipho), of the woody part of 

 the vascular bundles [Citrus Aurantium, Pastinaca pratensis Jord. ; 

 Madura aurantiaca, &c.), of sclerenchymatous cells which are often 

 mixed with woody fibres (Stypjhnolobium japonicum). At times, lastly, 

 tlie number of certain supplementary parts is diminished (rovcised 

 bundles of Calycanihus rrMcrophyllus.) On the other hand, the 

 I^eduucles of various species possess tissues or elements which aro 



• See this Journal, ante, p. 91. 



t GiaviH, A., ' UecLcTchiH AnatomiqiiesBur lc8 Organes Vege'tatifs do TUrtica 

 dioica,' 4to, Bruxollew, 188.5, 250 pp. and 2!^ pla. 

 X Si.fc Aiiicr. Jourti. Sci., xxx. (1885) pp. 84-5. 

 f Comptea Ueudua, xcix. (1884) pp. 108G-8. 



