656 SUMMABY OF CURRENT RESEARCHES RELATING TO 



in chloropliyll and starch, often accompanied by crystals of calcium 

 oxalate. 



From the period of their entry into the leaf the foliar bundles 

 present a return to their primary structure ; the vessels increase in size 

 jind diminish in number, with increase in the thickness of their walls ; 

 the large secondary vessels and the sclerenchyme sometimes reappear ; 

 the latter from reasons purely mechanical. In pinnatinerved leaves the 

 largest vessels are often found in the midrib at a certain distance from 

 the base of the lamina ; the vessels in the middle, and even towards the 

 apex of the lamina, are frequently larger than tliose towards the base of 

 the leaf. 



All these modifications appear to be in accord with the conducting 

 function of the bundles ; the large vessels in the petiole and principal 

 veins may be connected with the turgidity of the leaf. 



Anatomy of Floral Axes.*— M. Labarie has studied the differences 

 between the anatomical structure of ordinary stems and of the floral 

 axes in the same plant, which he find?, with great uniformity, as follows : 

 — In the pedicels the cortex is more developed, the vessels of the wood 

 more numerous and smaller, and the pith more developed than in the 

 vegetative axes ; and this applies not only to pedicels properly so called, 

 but also to the fruit-bearing axes, i. e. to those special small branches on 

 which alone in certain trees, such as apples and pears, the floial pedicels 

 are developed. 



Development of the Vascular bundles of Monocotyledons.f^ 

 Fraul. S. Andersson finds that the development of the vascular bundles 

 in Monocotyledons does not differ so widely from that in Dicotyledons 

 as has generally been stated ; and that there is, in fact, a close 

 resemblance in this respect between Liliacese and Eanunculacete. In 

 most of the larger groups of Monocotyledons there are genera in which 

 there is a distinct development of a cambium-zone at an early period, 

 which subsequently more or less completely disappears. This is 

 illustrated by examples from the various families. In Lilium there is a 

 distinct intermediate tissue between the xylem and phloem, composed of 

 a meristem which divides by tangential walls, and contributes to the 

 growth of the young bundle. This is also strongly developed in some 

 other genera belonging to the Liliace^e and to allied orders, while in 

 others it is almost completely suppressed. In the Graminese there may 

 be detected, even in old vascular bundles of Zea Mays, remains of a 

 cambium-zone composed of cells arranged radially between the xylem 

 and phloem. The same is the case with some palms. In aquatic 

 genera, such as those of Alismacese, Naiadacese, and Typhacese, the 

 vascular bundles are much more feebly developed. 



Secretioii'receptacles in the Cactacese.l — Dr. C. Lauterbaeh has 

 examined the structure and mode of formation of the mucilage and gum- 

 cells, crystal-cells, and laticiferous cells, in a large number of species 

 belonging to this order, preceding his description by a general account 



* Eech. s. I'anatoniie d. axes floraux, Toulouse, 1888. See Bonnier's Eev. Ge'n. 

 de Bot, i. (1889) p. 91. 



t Bill. K. Svensk. Vet. Akad. Handl., xiii. (1888) Afd. 3, No. 12. See Bot. 

 Ceritralbl., xxxviii. (1889) pp. .586 and 618. 



+ Bdt. Ceiitrfdbl., xxxvii. (1889) pp. 257-64, 289-97, 329-36. 369-75, 409-13 

 C2 pl«.). 



