ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1023 



and Chelidonium grown iu the dark, than under normal conditions. 

 Whether this is caused by the resorption of the solid particles contained 

 in the latex, the author was unable to determine. These solid particles, 

 consisting of resin, caoutchouc, &c., he believes to be actual products 

 of excretion, of no further use to the j)lant. They probably perform 

 a purely mechanical function. 



Spiral Cells of Nepenthes.* — Hcrren L. Kny and A. Zimmermann 

 have investigated the structure and functions of the elongated spiral 

 cells which are found iu the jiith and cortex of the stem and in all 

 parts of the leaves of Nepenthes jylujllamphora. With regard to function, 

 they conclude that the purpose of these structures is the storing up, 

 and possibly the uniform distribution, of water through the as- 

 similating tissue. They appear to have no mechanical function of 

 supporting the tissues in which they are found. 



Fibrovascular Bundles of Cycadeae.f — MM. J. Costantin and L. 

 Morot have determined the previously unsolved question of the origin 

 of the supernumerary fibrovascular bundles in Cycadeae, taking as 

 their example Cijcas siamensis. They find their origin to be in the 

 pericycle, like those of Dracsena and of the Chenopodiacese. The 

 successive layers formed by these bundles are not independent of one 

 another; the first is connected with the normal fibrovascular circle by 

 a certain number of anastomoses ; and the following layers are united 

 in the same wav with one another, so as to present a network of larger 

 or smaller meshes. These bundles, like those of Monocotyledons, 

 appear at a very early period at the base of the stem, in connection 

 with the adventitious roots. This was observed also in Encephalartos 

 Altensteinii and Ceratozamia mexicana. 



Relation of Annual Rings of Exogens to Age. J— Prof. D. P. 

 Penhallow, while hardly feeling justified in drawing decisive con- 

 clusions from his observations on this subject, considers that they 

 furnish certain indications which it may be well to state as a guide 

 to future and confirmatory observations. They are as follows : — 



1. The formation of rings of growth is chiefly detei-mined by 

 whatever operates to produce alternating periods of physiological 

 activity. In temperate climates, where the seasons are sharply 

 defined, these periods are determined by the seasons themselves, but 

 in tropical and sub-tropical latitudes other influences, recurring at less 

 regular periods, operate to determine them ; — therefore 



2. In cold climates, rings of growth are an approximately correct 

 index ()f age, but in warm climates they are of little or no value in 

 this respect. 



3. Even in cold climates there is not an absolute correspondence 

 between number of rings formed and years of growth. 



4. In warm climates the tendency is to obliteration of rings and 

 homogeneity of structure. 



5. The distinction of rings is essentially due to structural modifi- 



• Bcr. Deutsch. Bot. Geeell., iii. (188.5) pp. 123-8 (1 fig.), 

 t Hull. Kfjc. Bot. Franco, vii. (188.5) pp. 173-5. 

 t Canadian RecurJ of Science, i. (188.5) pp. 102-75. 



