52 SUMMARY OF CURRENT RESEARCHES RELATING TO 



genera and species of monopodial orchids. Among the more genera? 

 results arrived at, the following are the most important. The cells of 

 the epiderm vary greatly in form, and the development of the cuticle 

 is also verv various. Only one species is described as having a sharply 

 denned endoderm. The cortical tissue is commonly distinguished by 

 its altered appearance and by the lignified character of at least a portion 

 of it. The ground-tissue of the vascular cylinder is usually composed 

 of parenchymatous elements. The phloem-portion of the vascular 

 bundle is always protected by a bundle-sheath. The arrangement of the 

 vascular bundles is classified under three different types. There are 

 rarely any vascular bundles in the pith. 



Gall of the Monterey Pine.* — W. A. Cannon describes the injuries 

 inflicted on the leaves and leaf-bases of the Monterey pine (Pinus radiata 

 Don. P. insignis Loud.), by the larvae of a gall-fly belonging to the 

 Cecidomyiidae. The gall consists mainly of hypertrophied epidermal 

 tissue ; and the immediate and principal cause of the hypertrophy ap- 

 pears to be the response on the part of certain plant-tissues to the 

 parasite's demand for food. This is indicated by the gradual enlarge- 

 ment of the cells surrounding the parasite in a manner which corre- 

 sponds to its growth, and also by the unusual amount of food-material 

 which these cells contain. 



C4J Structure of Org-ans. 



Underground Flowers.f — E. TJle describes a shrub growing in the 

 neighbourhood of Rio de Janeiro, Anona rhizantha, which produces its 

 flowers and ripens its fruits entirely underground. Besides the open 

 flowers, it produces more or less completely closed cleistogamous flowers. 

 The former appear to be contrived for pollination by special insects. 



Nectaries of the Cruciferae. J — According to Dr. A. Villani, the 

 variations in the number and arrangement of the nectaries in the flower 

 of Cruciferae may be arranged in three principal groups, those in which 

 there are respectively four or two nectaries, or only one. In the latter 

 case the flowers are always very small, and the nectary central ; where 

 the number is four or two, the nectaries are arranged in a great variety 

 of ways in respect to the four longer or the two shorter stamens. In 

 the very wide-spread Alliaria officinalis, the nectaries go through two 

 stages. In the first stage, while the flower is expanded, they perform 

 the ordinary nuptial function of attracting insects which are useful for 

 pollination, and keeping off injurious insects, such as ants. But after 

 the perianth has dropped, the nectaries increase in size, and still con- 

 tinue to secrete nectar ; in this stage they attract ants in great numbers, 

 and become extra-nuptial. The same is the case with a species of Car- 

 damine, C. Chelidonia. 



Nectaries of the Cucurbitaceae.§ — Prof. G. Arcangeli states that in 

 Cucurbita maxima the male flowers remain open longer in wet weather 

 and later in the year, than in fine weather and earlier, to avail thern- 



* Amer. Nat,, xxxiv. (1900) pp. S01-10 (6 figs.). 



t Die Natur, xlix. (1900) pp. 270-3 (5 figs.). See Bot. Centralbl., lxxxiv. (1900) 

 p. 89. X Mulpighia, xiv. (1900) pp. 167-71. 



§ Bull. Soc. Bot, ItaL, 1899, pp. 198-204. 



