ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 733 



Structure and Development. 

 Vegetative. 



Meriphyte of the Cycads.* — H. Matte has studied the vascular 

 system of the leaf (the meriphyte of Lignier) in the Cycads. He finds 

 that, except in Cycas, the foliolar traces in the rhachis consist of several 

 bundles. The typical horse-shoe form is seen only in Cycas, Dioon, and 

 Ceratozamia, the majority of the species of Zamia, and some species of 

 Macrozamia. In Encephalartos, and species of Zamia and Macrozamia 

 the foliar arc shows in the base of the petiole a complication which may 

 be considerable, and which is due to tensions and bundle-displacements 

 which are caused by foldings of the foliar arc. The arc in Stanyeria and 

 Bowenia differs from that in the other genera previously mentioned ; 

 that of Bowenia has the same form as that of Anyiopteris. The form of 

 the foliar arc in young leaves is generally simpler than in mature ones, 

 on the study of which the results given were based. 



Sap-excreting Elements in Tropaeolum majus.f — G. Irgang shows 

 that the drop of clear sap which appears on the wound when the stem, 

 leaf-stalk or blade of Tropaiolum majus is cut, comes from the young 

 vascular bundle-elements which remain for a remarkably long time un- 

 lignified, thin-walled and very rich in sap. Towards the top of the stem 

 almost all the vascular elements are unlignified ; as we descend the 

 stem the proportion diminishes, hence in the older parts of the stem 

 the exudation of sap is less in quantity. In the epidermis of the upper 

 and under leaf -surface occur mucilage-cells characterised by their size, 

 contour, and cell-contents. 



Regeneration of the Assimilating Mechanism in Streptocarpua 

 and Monophyllsea.J — F. Pischinger gives the following results of his 

 experimental study. In Streptocarpus and Monopliylltm the cotyledons 

 are of unequal size when in the seed. In S. Wendlandi there is at the 

 base of the larger cotyledon a small-celled meristem, which during 

 germination enlarges, and later forms the secondary leaf-like growth of 

 the single leaf of the plant. The axis of the inflorescence subsequently 

 develops from a definite portion of the same meristem ; since this meri- 

 stem is derived directly from the meristematic tissue of the embryo, the 

 inflorescence cannot be regarded as an adventitious structure. Similarly, 

 the apparent leaf -stalk of the larger cotyledon must be regarded as an 

 axial organ united with the stalk, and this holds also for the species 

 which form leaf-rosettes. 



In the one-leaved S. Wendlandi not only does regeneration of the 

 larger cotyledon occur if its basal meristem remains either entirely or in 

 part, but the whole cotyledon will re-form if cut away ; and frequently 

 the smaller cotyledon becomes stimulated to stronger growth by de- 

 struction of the larger and forms a secondary leaf -like growth, or the 

 plant may be induced to form new true foliage-leaves. On the other 

 hand in S. Gardeni, which forms leaf-rosettes, no regeneration of the 



* Ooroptes Eendus, cxxxvii. (1003) pp. 80-2. 



+ S.B. k. Akad. Wiss. Wien, cxi. (1902) pp. 723-1 (1 pi.). 



% Tom. cit., pp. 278-300 (2 pis.). 



Dec. 10th, 1903 3 b 



