16:t 



SCIENCE 



[N. S. Vol. XXXVIII. No. 970 



convincing the uninformed that malaria-con- 

 trol through the control of mosquitoes is not 

 only possible, but that it pays. While the in- 

 accuracies do not materially detract from the 

 practical value of the book, it is to be hoped 

 that in the interest of truth they will be cor- 

 rected in a future edition. 



Frederick Knab 

 Bureau of Entomology 



SPECIAL AUTICLES 



THE ORIENTAL CYCADS IN THE FIELD 



Cycads in the field, cyoads in the botanical 

 garden and cycads in the greenhouse, are so 

 different that descriptions based upon plants 

 growing in the garden should be checked by 

 observations in the field, and accounts based 

 upon greenhouse material must be viewed 

 with great suspicion. 



In the field, Cycas circinalis is said to pro- 

 duce a crown of leaves every year, and under 

 ordinary greenhouse conditions, new crowns 

 are usually produced every year; but where 

 the heat is extreme and the rainfall excessive, 

 two crowns each year may be produced for 

 many years in succession. Dioon at Kew sur- 

 passes anything I have ever seen at Cliavar- 

 rillo, but if the Kew specimens should be ex- 

 posed to the blazing sun of the Mexican trop- 

 ics, their magnificent crowns would probably 

 wither in a few days. In cycad seedlings at 

 the University of Chicago, scale leaves, which 

 in the field would never have been anything 

 but scale leaves, quite regularly develop into 

 foliage leaves. The cycads, like roses, pinks 

 and chrysanthemums, may appear to better 

 advantage on account of greenhouse condi- 

 tions, but for phylogenetic studies, their value 

 is doubtful. 



During the past year it was my privilege to 

 study in the field the five oriental genera of 

 cycads. Two of these genera are found only 

 in South Africa, two only in Australia, and 

 the remaining genus, Cycas, extends from 

 Japan to Australia and Madagascar. Thus 

 all the oriental cycads, except Cycas, are con- 

 fined to the southern hemisphere; while all 

 the western cycads, except Zamia, are confined 



to the northern. No genus is common to the 

 east and the west. 



The three genera found in Australia are 

 Cycas, Bowenia and Macrozamia. All three 

 are abundant in Queensland, the northeast 

 part of Australia, and Cycas and Bowenia 

 may be confined to this region; Macrozamia 

 extends into New South Wales and is repre- 

 sented by at least one species on the western 

 coast. 



Cycas, in Australia, is represented by five 

 species, only one of which, Cycas media, was 

 studied in the field. The other three were 

 seen in gardens. Cycas media was studied at 

 Rockhampton, on the Tropic of Capricorn, 

 and at Freshwater, in the Cairns district, 

 about 700 miles farther north. 



Eichler's account, in Engler and Prantl's 

 " Die Natiirlichen Pflanzenfamilien," gives 

 Cycas media a height of 20 meters, making it 

 the tallest of the cycads. This is undoubtedly 

 a mistake. Dr. F. M. Bailey, in his " Flora 

 of Queensland," states that the species reaches 

 a height of 8 to 10 feet (2.4 to 3.05 meters) 

 and sometimes twice that height. Mr. Sim- 

 mons, director of the Botanical Garden at 

 Rockhampton, and Mr. Anderson, director of 

 the Botanical Garden at Townsville, assured 

 me that the plant seldom exceeds 3 meters in 

 height and that specimens 6 meters in height 

 were extremely rare. Mr. Sydney Snell, who 

 for many years has lived and hunted in the 

 Berserker Ranges near Rockhampton, showed 

 me the tallest specimen he had seen, and it 

 measured about 6 meters. I received similar 

 reports all the way from the southern to the 

 northern limit of the species. At Freshwater, 

 in the Cairns district, I found one plant which 

 ■was 7.01 meters in height. The mistake in 

 Eichler's account probably arose in mistaking 

 feet for meters. 



A section of the trunk shows the polyxylic 

 condition, but a specimen 2 meters high shows 

 only two or three zones of wood, while a speci- 

 men of Cycas revoluta half a meter in height 

 might show as many as three or four. 



The trunk is ribbed, like that of Dioon 

 spinulosum, and the ribs are due to the alter- 

 nation of foliage leaves and scale leaves or 



