110 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Interruption in the Pith of Coniferse.* — Herr C. Fritsch has deter- 

 mined that this phenomenon is due, not to external causes, but to changes 

 in special groups of cells, ending in tbeir complete disapi^earance. The 

 cavities formed in this way are never filled with turpentine or resin. 

 The phenomenon is confined to the genera Picea, Abies, Larix, and 

 Cedrus, and is not found in all species of these genera. 



Ant-entertaining Plants, f — In addition to the plants enumerated 

 by Beccari J as being inhabited by ants, Herr H. Karsten describes another, 

 Cecropia peltata, in which the ants inhabit peculiar cavities in the internodes 

 formed by a peculiarity in the growth of the plant. In those specimens 

 in which ants have taken up their abode, these cavities are connected with 

 one another by circular perforations, while in those which are not so 

 inhabited, the cavities remain distinct. 



Laticiferous Vessels. § — Sigg. Pirotta and MarcatHi have studied the 

 distribution and relations of the laticiferous system in a number of orders, 

 with the general result of corroborating the suggestions of Haberlandt. ]1 

 (1) In Apocynaccse the laticiferous vessels are distributed in a twofold 

 manner within the leaf, (a) The vessels follow the veins to their last 

 ramifications, forming a fine net in the parenchyma, and coming into more 

 or less direct connection with the assimilating cells, (fc) After accom- 

 panying the bundles so far, the laticiferous vessels leave them, penetrate 

 freely into the parenchyma of the mesophyll, and. become ajDplied to the 

 assimilating cells. (2) In Ascleinadaceae (a) with reduced or modified 

 leaves, the very numerous laticiferous vessels run in all directions through 

 the assimilating subepidermal parenchyma of stem and branches, exhibiting 

 close connection with the assimilating cells, (b) In those with normal 

 leaves the connections between assimilating cells and the laticiferous vessels 

 are much more manifest. They follow the veins and then part from them, 

 traversing the parenchyma and frequently penetrating between the pali- 

 sade-cells. (3) In Eujjhorhiacese (a) with reduced modified leaves the 

 laticiferous vessels are cortical or medullary, but always in close con- 

 nection with the assimilating cells, (fe) In those with normal leaves the 

 laticiferous vessels follow the vascular bundles for some distance, and then 

 leave them, becoming isolated and exhibiting intimate connections with the 

 green cells. (4) In Campanulaccse and (5) Loheliacese the vessels either 

 accompany the bundles to their fine terminations, or traverse the paren- 

 chyma, often ending in the spongy tissue, surrounded by a considerable 

 number of conducting cells. (6) In Papaveracese the laticiferous vessels 

 follow the bundles and end with them, or else traverse the spongy tissue, and, 

 passing between the palisade cells, end finally below the epidermis. (7) In 

 Ai-aceae the laticiferous vessels frequently ramify in the parenchyma, or 

 pass between the palisade cells to the epidermis. (8) In Musa the laticiferous 

 vessels never leave the bundles, but become associated with the palisade cells. 



(5) Structiire of Organs. 



Origin and Development of the Lateral Roots in Dicotyledons. f — 

 According to M. A. Lemaire, the immense majority of the lateral roots of 



* Schrift. K. Phys.-Oek. Gesell. Konigsberg, xxv. (1885). See Bot. Centralbl., xxvii. 

 (1886) p. 218. 



t Flora, Ixix. (1886) pp. 304-6. J See this Journal, v. (1885) p. 484. 



§ Key. Ital. Sci. Nat., ii. (1886) pp. 60-1, from Ann. 1st. Bot. Koma, ii. (18»G). 

 II See this Journal, 1883, p. 868. 

 \ Ann. Sci. Nat. (Bot.), iii. i;i886) pp. 163-272 (6 pis.). 



