NOTES AND ABSTRACTS. 



NOTES AND ABSTRACTS. 



Agave fourcroydes Lem. By A. Berger (Bot. Mag. t. 8746; 1918). — Native 

 of Yucatan. The species which supplies from its leaves the fibre known as 

 Henequen. It is grown in most tropical and semi-tropical countries, and is 

 sometimes used as a hedge plant. Reproduction is provided for by seeds, 

 viviparous bulbils which arise on the panicle, and also by suckers. The in- 

 florescence is 18-21 feet high, slightly curved at the top. The flowers are 

 yellowish-green, 2^-3 inches long. — L. C, E, 



Alnus flrma Sieb. et Zucc. var. Yasha. By S. A. Skan (Bot. Mag. t. 8770; 



1918) . — Native of Japan. A small tree belonging to the section of the genus 

 characterized by having the female inflorescences in terminal racemes, which 

 make their appearance in spring. The leaves are ovate-lanceolate, glabrous 

 above, adpressed pubescent beneath, lateral nerves ten to sixteen on each side 

 of the midrib, nearly parallel. Male catkins, solitary or in pairs, female catkins 

 in terminal racemes of two to five together, — L. C. E, 



Angraeeum graeilipes Rolfe (Bot. Mag. t. 8738; 1918). — Native of Mada- 

 gascar. A species first grown in this country under the name of A. recurvum, 

 from which it differs in its greatly elongated pedicels and its much larger leaves. 

 A . graeilipes thrives well under the same treatment as that required for A . 

 eburneum. The flowers are white and very showy. — L. C. E. 



Aphides, Apple. By F. V. Theobald (Jour. Bd. Agr. vol. xxvi. No. 1, April 



1 91 9) . — A full account of the following three of the four aphides of general 

 importance recorded as attacking the apple in Great Britain : — Blue Bug or 

 Rosy Apple Aphis (Aphis malifoliae), Green Apple Aphis (Aphis pomi), and 

 the Oat Apple Aphis (Siphocoryne avenae). The fourth, which is not treated 

 in this article, is the Woolly Aphis or American Blight. The life histories are 

 given, and an account of the damage done. Prof. Theobald advocates " pre- 

 ventive treatment " in autumn, either by spraying or dusting trees to kill 

 exposed oviparous females and prevent egg-laying. It must be thoroughly 

 done, as a few females left will deposit eggs from which numerous young will 

 be produced the following spring. Spraying in spring, when buds are swelling, 

 with a wash compound of 1 to cwt. lime, 5 lb. salt, 100 gallons water, is 

 also advocated, as this kills newly-hatched aphides, while those hatched later 

 are prevented from entering the opening buds. Soft-soap and water, nicotine, 

 or pyridine are all recommended for use later. — G. C. G. 



Aphids, Economic, Alternation of Hosts in. By W. M. Davidson (Jour. Econ. 

 Entom. vol. xi. June 191 8, pp. 289-294). — Of the twenty-one economic species 

 with alternate host habits mentioned in this paper, at least fourteen are common 

 to Europe as well as America. 



Whilst the author is considering these aphids' habits in America only, the 

 alternate hosts are of interest here. 



The Hop Aphis (Phorodon humili) alternates between hop and plum. Black 

 Cherry Aphis (Myzus cerasi) between cherry and Lepidium. Bean Aphis (Aphis 

 rumicis) feeds in summer on Leguminous and Chenopodiaceous plants. Woolly 

 Aphis (Eriosoma lanigerum) apple and pear, and passes the winter in a dormant 

 state on elms. Oat Aphis (Aphis prunifoliae) reproduces all the year round in 

 semi-tropical zone and winters in the north on apple. Peach Aphis (Myzus 

 persicae) has a long list of hosts, mostly cultivated plants. 



Many species are of economic importance at one period of the year only. 

 The alternating host being a weed, it provides another excellent reason why 

 certain weeds at least should be destroyed. Examples of such aphides are : 

 Rhopalosiphon lactucae, which migrates between currant, gooseberry, and sow- 

 thistle (Sonchus). Aphis malifoliae, apples, rib-grass, and plantains. Hyalo- 

 pterus arundinis, the mealy plum aphis which passes the summer on reeds. The 

 paper concludes with a useful bibliography covering two pages. — G. W. G. 



