RemarTcs on the Natural order Cycadea. 45 



The Jirst, second and third experiments indicate, in the tenth 

 column of the preceding table, that beyond a certain limit the ratio 

 of IV eight of metal to extracting force begins to diminish, showing 

 that it would be more economical to increase the number rather than 

 the length of the spikes, for producing a given effect in fastening 

 materials together. In this case, also, it will be perceived, that the 

 adhesion has a much closer relation to the areas of the compressing 

 faces of the spikes, than to their weights. For three of the experi- 

 ments this ratio may be regarded as identical, and dividing, for each 

 of the five experiments, the observed retention by the area of the 

 two faces opposed to the ends of the fibres, we get a mean result, 

 which proves that the absolute retaining povi^er of unseasoned chest- 

 nut, on square or flat spikes of from 1.8 to 3.9 inches in length, is 

 about 813 lbs. for every square inch of those faces which condense 

 longitudinally the fibres of the timber. 



Art. IV. — Remarlcs on the Natural order Cycadece, with a descrip- 

 tion of the ovula and seeds of Cycas revoluta, Willd. ; by A. J. 

 Downing. 



[Read before the L3'-ceum of Natural History, New York, Oct. 17, 1836.] 



Cycas revoluta, figured in the accompanying plate, (Plate I.) be- 

 longs to a genus comprising but four other known species, which to- 

 gether with Zamia constitute the Cycadece, one of the smallest but 

 most interesting orders in the whole vegetable kingdom. Their sin- 

 gular structure and manner of growth, their simple cylindrical stems 

 and crowning tufts of foliage, like some of the Palms, and their 

 commonly gyrate vernation, like that of most Ferns, as well as their 

 anomalous inflorescence and fructification, have rendered them ob- 

 jects alike of the greatest interest and perplexity to the learned bot- 

 anists who have examined them. 



Cycas circinalis, Willd., a native of Malabar and Japan, seems 

 to have been the first species discovered, having been described by 

 Rheede, as early as 1682.* Rumphius,f in 1741, figured and de- 

 scribed it under the name of Olus calappoides : he remarks its re- 

 semblance to the arborescent Ferns, and thinks it might with pro- 

 priety be called Osmunda arhorescens. Linneeus, who first gave the 

 genus its present name, seems, from the imperfect manner in which 

 its structure was known in his time, to have been greatly at a loss 



* Hon. Malab. vol. iii, p. 9. t Herb. Amboiense, vol. i, p. 87. 



