88 RESEARCHES ON FUNGI 



Strasburger J they are not persistent nuclear spindle-fibres, but 

 are secondary formations which grow through the primary cell- 

 wall after this has become completely formed but before the 

 deposition upon it of thickening layers. This mode of origin, 

 which is not dependent upon nuclear division, permits of plasmo- 

 desmae being formed between such tissues as the epidermis and the 

 outer cells of the cortex 2 and between the living cells of a scion 

 and its stock. 3 In the Fungi, as we shall see, the protoplasmic 

 bridges between the cells, except in so far as fusions between 

 different hyphae are concerned, are not secondary but primary. 



In the Red Algae, the Brown Algae, and certain Green and Blue- 

 green Algae, there are pits between adjacent cells ; and, where 

 such pits occur, it is probable that there is protoplasmic continuity 

 between neighbouring cells. 4 Arthur Meyer 5 demonstrated proto- 

 plasmic continuity in three species of Volvox in 1896. According 

 to Falkenberg 6 the pits of the Florideae have closing membranes 

 which, when isolated, appear punctate and bear minute protoplasmic 

 fibrillae, thus suggesting that, under normal conditions, they are 

 threaded by very fine plasmodesmae. In the Laminariaceae, sieve- 

 tubes were discovered by Reinke 7 in 1876 and, subsequently, they 

 were studied by Wille, Will. Rosenthal, Oliver, and others. 8 Sykes, 9 

 in 1908, as a result of investigations made with the most modern 

 technique, came to the conclusion that, in Macrocystis pyrifera 



and of the adult stem, leaf, and root of P. sylvestris, including the root-cap and the 

 junction of the endodermis with the cortex in a leaf. Strasburger. in his masterly 

 paper, solved problems connected with the origin of plasmodesmae. 



1 E. Strasburger, loc. cit., pp. 493-503. 



2 Ibid., pp. 495-500. 3 Ibid., pp. 582-585. 



4 For references to the literature on plasmodesmae in Algae, vide F. Oltmanns, 

 Morphologie und Biologie dcr Algen, Aufl. 2, Jena, Bd. Ill, 1932, pp. 5-6. 



5 A. Meyer, " Die Plasmaverbindungen und die Membranen von Volvox globator, 

 aureus und tertius, mit Riicksicht auf die thierischen Zellen," Bot. Zeit., Bd. LIV, 

 1896, pp. 187-217. 



6 P. Falkenberg, " Rhodomelaceen des Golfes von Neapel," Fauna und Flora, des 

 Golfes von Neapel, Berlin, 1901, pp. 16-27. 



7 J. Reinke, " Beitrage zur Kenntniss der Tange," Jahrb. f. wiss. Bot. Bd. X, 

 1876, p. 373. 



8 For references to this series of papers, vide Sykes. 



9 M. G. Sykes, " Anatomy and Histology of Macrocystis pyrifera and Laminaria 

 saccharina," Annals of Botany, Vol. XXII, 1908, pp. 291-325. 



