410 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ligneous Tumours in the Vine.* — M. E. Prillieux states that fre- 

 quently viues may be seen covered with ligneous tumours formed of a 

 number of small nodules aggregated together. These bodies, which have 

 a diameter of 6-8 cm. and a length of 15-20 cm., arise beneath the 

 fibres of the cortex. The author states that they arise from hyper- 

 trophy of the young tissues on certain points in the old wood. 



Cuscuta Gronovii.t — Miss H. E. Hooker describes the mode of 

 parasitism of one of the common dodders of the northern United States, 

 Cuscuta Gronovii. The seeds are exalbuminous, of comparatively large 

 size, with a conspicuous hilum and hard testa ; but the latter yielded 

 readily to soaking in dilute potash, and careful dissection removed the 

 two coats and freed the coiled vermiform embryo. The haustoria are, 

 outwardly, enlarged fleshy discs, and differ from true roots, as does the 

 root^acting end of the stem, in the absence of a root-cap. There is very 

 little differentiation in the tissues of the dodder ; the vascular system 

 consists of alternate strips of tracheides and parenchyme, each about 

 two rows of cells wide, and, in the best developed stems, occupies 

 perhaps from one-third to one-half the diameter. Of the adventitious 

 buds the author only studied those producing branches. The regular 

 branching of a stem of Cuscuta is abnormal in the centrifugally arranged 

 accessory buds, the last-formed bud being farthest from the parent stem, 

 though sections show it to originate in the axillary bundle. The 

 epiderm of the dodder varies with its position. On the long internodes 

 between adjacent scales stomates are rare, while over haustoria, i. e. on 

 the side of the stem opposite them, very small stomates are quite abun- 

 dant. Each flower has a short pedicel resembling the main stem in struc- 

 ture, a thickened receptacle, a five-lobed calyx and corolla, and adherent 

 stamens alternating with its lobes ; the ovary is bilocular with two ovules 

 in each locule, and there are two knob-like stigmas on short styles. 



Vegetative Organs of Bignoniaceae, Rhinanthacese, Orobanchese, 

 and TJtricnlariacese.l — M. M. Hoveiacque describes in great detail the 

 structures included under these heads. The following are some of the 

 more important generalizations : — 



The phloem shows a series of gradually increasing complications in 

 structure from the annual Ehinanthacege through the woody BignoniacesB 

 to the Orobancheee, In the xylem there is a corresponding series of 

 stages in complication, the most perfect condition being found in the 

 Bignoniacese, the simplest in the Utriculariacese. 



In the leaves we find the most highly developed internal structure in 

 the woody and climbing Bignoniaceae, such as Catalpa and Eccremocarpus, 

 Those of Uiricularia are very simple, bnt exhibit a striking dimorphism. 



The orders under discussion do not belong to any common type as 

 respects their vegetative organs, A certain resemblance is, however, ex- 

 hibited in the stem of Bignoniaceae and Rhinanthacere ; but the former 

 are of higher organization, and show some affinity to the Scrophulariaceae. 

 The Lathrseese resemble the Ehinanthacese in all their anatomical 

 peculiarities ; the Orobanchese display but little affinity to the Lathrseese, 



* Bull. Soc. Bot. France, xxxv. (1888) pp. 393-5. 



t Bot. Gazette, xiv. (1889) pp. 31-7. 



X ' Rech. sur I'appareil ve'g. d. Bignouiacees, Rhinantbaee'es, Orobanchees et 

 L'trieularie'es,' 8vo, Paris, 1888,, 765 pp. and 651 figs. See Bot. Centralbl., xxxvii, 

 (1889) p. 17, 



