ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 255 



and in Platanus. That the increase in the size and number of the 

 vascular bundles is directly incited by the weight of the fruit, is shown 

 by the fact that when female flowers remain unfertilized, as is the case 

 with large numbers in the oak, walnut, and horse-chestnut, the axis 

 retains the structure characteristic of that of fugacious male flowers. 



In the case of neuter flowers, the structure of the axis varies accord- 

 ing to that of the flower itself. Where sterility results from the con- 

 version of stamens into petals, as in the case of the double tulip, the 

 scape is twice as thick as in the case of a single flower, and has a 

 correspondingly increased number of vascular bundles. When, as in 

 Hydrangea and Viburnum Opulus, the sterile flowers are fugacious and 

 simply for the purpose of display and of attracting insects, the axis has 

 the characters of that of male flowers. 



Comparative Anatomy of Flowers.* — Eev. G. Henslow follows up 

 previous observations on the relation of floral organs to their vascular 

 cords or " axial traces." Taking the cords as " floral units," the author 

 suggests their relation to axes as well as to all kinds of floral appendages. 

 The two elements of a cord are tracheae or spiral vessels and sieve- 

 tubes, &c, or soft bast ; Van Tieghem's distinction between axial and 

 foliar characters of cords is not constant. Mr. Henslow discusses the 

 origin of umbels in exogens and in endogens, the influence of the union 

 of the cords on phyllotactical arrangement, the multiplication of parts 

 arising from the " chorisis " of a cord, the undifferentiated state of organs 

 when in congenital union, the non-axial character of almost all placenta- 

 tion, &c. The free-central placentation of Priinulaceaa is interpreted as 

 due to the coherent and ©villiferous bases of five carpels, which have the 

 upper parts of their margins cohering in a parietal manner and without 

 ovules. The author proposes continuing his observations. 



Floral Nectary of Symphoricarpus.f — Prof. F. Delpino corrects a 

 mistaken description by H. Miiller, Bonnier, and others, of the floral 

 nectary in Symphoricarpus racemosus. The purpose of the hairs which 

 clothe the tube of the corolla he states to be, not to protect the nectar 

 from rain, but to prevent the entrance of insects which would be in- 

 jurious by feeding on the nectar without assisting in the pollination of 

 the stigma, especially of ants. 



Fruit of Borraginese.f — Friiulein A. Olbers describes five different 

 kinds of fruit and of the structure of the pericarp in Borraginea?. This 

 is connected also with differences in the structure of the " foot," which 

 Friiulein Olbers believes to have no function, in general, in connection 

 with the storing up of water for germination, but rather with the bursting 

 and detachment of the fruit. 



Explosive Fruits of Alstrcemeria.§ — Dr. O. Stapf describes the 

 structure of the ripe capsule of Alstrcemeria psiitacina, and the cause of 

 its violent rupture. This depends on the differentiation of the develop- 

 ment of different layers of the placenta, which consists eventually of 

 three horny clasps, firmly attached at the apex to the lobes of the 

 capsule, and separated by thin-walled parenchyma. Finally, these clasps 



* Proc. Roy. Soc, xliii (1S87) pp. 296-7. t Malpighia, i. (1887) pp. 434-9. 

 t SB. Bot. S'allsk. Stockholm, May 31, 1887. See Bot. Ceutralbl., xxxiii. (1SSS) 

 p. 88. 



§ SB. K. K. Zool.-Bot. Gesell. Wieu, xxxvii. (1887) pp. 53-5. 



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