812 SUMMARY OF CURRENT RESEARCHES RELATING TO 



carbon dioxide and water, and to believe that by polymerization a 

 substance is produced wbicb can combine with the nitrogenous resi- 

 dues of previous dissociations of proteid to reconstitute proteid. He 

 does not agree with the suggestion of Loew and Bokorny that the 

 methyl aldehyd may combine with ammonia and sulphur to form 

 proteid de novo. 



Lastly, Professor Strasburger makes a suggestion as to the probable 

 physiological significance of the nucleus. He points out that the 

 nucleus cannot be regarded as regulating cell-division ; for instances 

 are known of cell-division taking place without previous nuclear 

 division, and, conversely, of nuclear division taking place without 

 cell-division. He is of opinion that the nucleus plays an important 

 part in the formation of proteid in the cell. This view is founded 

 upon the facts that one or more nuclei have been found to be present 

 in the vast majority of plant-cells, that the nucleus is, as a general 

 rule, the most persistent protoplasmic structure, and that it gives the 

 various proteid reactions in a very marked manner. 



Order of Appearance of the Primary Vessels in Aerial Organs.* 

 — A. Trecul has collected the results of a long series of observations 

 on the formation of the first vessels in the stem, leaves, and floral 

 organs of the following plants : — Anagallis arvensis, Primula elatior, 

 officinalis, grandiflora, and other species, Lysimachia, Buta, Lupinus, 

 Astragalus, Galega officinalis, Fosniculum vulgare and dulce, Iris, 

 Allium, Funkia, Hemerocallis, and a number of grasses. For the 

 details of the observations reference must be made to the paper itself. 

 Among the more important of the general results, M. Trecul is led 

 to contest the usual statement that all stems and leaves branch from 

 below upwards, and especially Sachs' explanation of the pinnate and 

 other forms of division in leaves as referable to a scorpioid type. 

 The order of appearance of the vascular bundles shows, on the con- 

 trary, that there are two kinds of pinnate leaves, basifugal or 

 acropetal, and basipetal ; and the same is true of leaves where the 

 segmentation is not carried so far ; and also of the secondary divisions 

 of the leaflets themselves. The basipetal development may also be 

 altogether independent of any scorpioid arrangement. 



Collenchyma. j — An examination of the structure and mode of 

 formation of collenchyma in a large number of plants, made by C. 

 van Wisselingh, confirms the general statement of Sachs, that this 

 tissue has its origin directly in the fundamental tissue. In all the 

 plants examined by him the vascular bundles were already in exist- 

 ence in the procambial condition before the formation of the collen- 

 chyma. He found no instance of the common origin of collenchyma 

 and mestome described by Haberlandt and Ambronn. The number 

 of layers of cells found in the youngest state between the epidermis 

 and vascular bundles varied from two to six, or even more. 



Most commonly, in the tissue intermediate between the epidermis 



* Ann. Sci. Nat. (Bot.) xii. (1882) pp. 251-381. 



t Arch. Neerland. Sci., xvii. (1882) pp. 23-58 (2 pis.). Of. this Journal, i. 

 (1881) d. 768. 



