ZOOLOaY AND BOTANY, MICKOSCOPY, ETC. 245 



the electric light is particularly rich in blue and violet rays. The 

 author considers the electric light employed as too feeble to allow of 

 any conclusion as to the necessity of a nocturnal rest to plants. It 

 was, however, evident that the electric illumination during the night 

 was advantageous to those plants which passed the day in the rather 

 feeble diffuse daylight of the palace. In a third series of experi- 

 ments, the intensity of the electric light was practically augmented by 

 placing the plants nearer the lamp. The experiment was again fatal 

 to young seedlings receiving the electric light exclusively, but many 

 of the hardier and more mature plants survived, although the leaves 

 of some were blackened by their too great proximity to the light ; and 

 again the nocturnal electric illumination was decidedly favourable to 

 the plants which passed the day in the light of the palace. The 

 author sums up his conclusions thus : — 



1. The electric arc-light emits radiations which are injurious to 

 vegetation. 



2. Most of these radiations are arrested by colourless glass. 



3. The electric light emits radiation powerful enough to maintain 

 mature plants in vegetation for two months and a half. 



4. The beneficial radiations are not sufficiently powerful to cause 

 the growth of germinating seeds, or to allow of the maturation of 

 fruit in older plants. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Peculiar Form of Stereome in Ferns.* — E. Giltay describes a 

 peculiar form of sclerenchymatoiis cells in Aspidium {Polystichum) 

 Berteroanum, occurring free in the rhizome in the fundamental tissue, 

 and usually hardened on one side only. These cells were in contact 

 with one another by their thickened sides, the unthickened sides 

 being in contact with the surrounding thin-walled parenchymatous 

 cells. Continuous hard ridges are thus formed in the fundamental 

 tissue, which must contribute considerably to the firmness of the 

 organ. This hardened tissue is usually found near the fibrovascular 

 bundles, often reaching to the endoderm, and appears to perform the 

 function of a protecting sheath. 



These half-sclerenchymatous half-parenchymatous cells are filled 

 with starch like the surrounding thin-walled cells ; they were usually 

 of large size. Occasionally a few that were associated with them 

 were completely sclerenchymatous. 



Of a large number of species of ferns examined, only the one 

 already named and Aspidium (Polysticliwrn) Bichardi contained these 

 half-sclerenchymatous cells ; in all the other species they were either 

 entirely wanting or only faintly indicated. 



Structure and Branching of Dorsiventral Polypodiacese.f — 

 According to L. Klein, in Polypodium Heracleum and quercifolium, 



* Bot. Ztg., xl. (1882) pp. 694-7 (1 pi.). 



t Klein, L., ' Bau u. Verzweigimg einiger dorsiventral gebauten Polypodia- 

 ceen.' Halle, 1881, 64 pp. 



