50 THE JOURNAL OF BOTANY 



long narrow cells, present in the normal tliallus jnst below the 

 superficial layer, become considerably elongated. The superticial 

 position of the gall, together with the long narrow form of these 

 ceils, suggests at first sight a parasitic alga with penetrating fila- 

 ments. The cells of the gall exhibit walls of C(»n.>iderable tnickness, 

 together with dense granular cont^nis. In the largest galls the 

 tissue is to a certain extent destroyed by the nematodes which are 

 present among the cells. The fact that the young gall remains 

 intact may be explained by a rapid growth taking place while the 

 animal is still buried m the main thallus. In order to escape, 

 the nematode would afterwards have to force its way through 

 the close structure of the mature gall, thereby tearing it apart. 

 The galls sometimes arise close together, and as each one equals 

 or exceeds in size the diameter of the main thallus, a group of them 

 forms a conspicuous, irregular knob. 



The granules referred to above as occurring in the cells below 

 and around the growing gall differ very much both in size and form 

 from those of the ordinary thallus-cells. Their form is oval or 

 round, and their diameter from 4 /x to 7 /x. They are of a clear 

 and slightly retractive nature, having the appearance of small 

 starch-grains, but showing no concentric structure. In polarized 

 light they show the well-known black cross characteristic of starch- 

 grains. Under the action of acids and alkalies they swell up, and 

 soon dissolve completely ; with iodine they take on a brown tint 

 slightly deeper than that of the surrounding cell-contents, but after 

 heating in water to 100° 0. for a short time (presumably after 

 hydrolysis of the substance of the granule) application of iodine 

 produces a bluish-purple tint. 



Since these structures agree in all respects, except for the 

 prersence of concentric layers, there can be little doubt that they 

 are identical with the granules described by Prof. Van Tieghem as 

 Floridean starch." They probably consist chiefly of amylodextrin.f 

 It is interesting that structures which occur in the normal cells of 

 FloridecB should be found in Furcellaria only in those cells which 

 have been stimulated by the action of the nematodes. 



Among the slides in the ISchmitz collection at the British 

 Museum are three of Furcellaria fastigiata, labelled " Knollchen- 

 Johnson." The sections are very deeply stained and rather 

 imperfect, but, so far as can be seen, the galls appear to be the 

 same as those I have described, though I can detect no actual 

 nematode. 



The material of Chondrus crispiis, which showed galls as the 

 result of attack by nematodes, was so scarce that it has not been 

 possible to make a full examination of them. So far as can be 

 seen, a similar process takes place, but whether the same peculiar 

 cell-contents are found in the young stages I do not know, as none 



* Van Tieghem, •' Sur les globules amylaces des Floridees et des Coral- 

 linees," Comptes Rendus^ xi. 804 (1865). 



t Arthur Meyer in Botanische Zeitimg, 1886, pp. 697, 713. 



