HISTORY OF PILOBOLUS 



17 



divisions but, finally, nuclear division ceases. Cell-division, however, 

 continues until the masses are cut up into regular oblong binucleate 

 cells (Fig. 8, D). The primary cleavage resulting in protospores is 

 complete about 4 a.m., and the period of embryonic growth and divi- 

 sion lasts until about 7 a.m. The binucleated spores (e), which at first are 

 naked masses of protoplasm, soon be- 

 come covered by a wall, and drops of 

 oil appear in their interior. The ripe 

 spores lie embedded in a shining mass 

 of intersporal substance (/) which can 

 be stained readily with gentian violet 

 and which appears to be nothing more 

 than an excretion of the protoplasm 

 made during the ripening of the spores. 



The spores (Fig. 8, E), when sown, 

 swell tremendously (Fig. 8, F) before 

 pushing out a germ-tube, and the two 

 nuclei soon divide to form eight or more 

 which may be seen in the sporeling 

 when the germ- tube is still very short 

 (Fig. 8, G). The mycelium is unicellular 

 and multinucleate. When a sporangio- 

 phore is to be formed, the protoplasm 

 collects at a point in the mycelium and 

 there forms a barrel-shaped swelling. 

 This swollen portion is cut off from the 

 rest of the mycelium (in the species 

 studied) by both peripheral and proxi- 

 mal walls. The division of the protoplasm is accomplished by simple 

 constriction furrows ; and in the bulb so formed, as already 

 mentioned, a rapid multiplication of nuclei takes place. 



Crystalloids.— In 1872, Klein ^ discovered crystalloids in the 

 sporangiophore of Pilobolus ; and, in 1875, van Tieghem 2 found 

 that these bodies are present not only in Piloboli (Fig. 9) but in 

 a large number of other Phycomycetes, e.g. Phycomycetes nitens, 



1 J. Klein, he. cit., p. 337, Taf. XXIV, Fig. 23. 



2 P. van Tieghem, " Nouvelles recherches sur les Mucorinees," Ann. Sci. Nat., 

 6ser.,T. I, 1875, pp. 24-32. 



VOL. VI. 



Fig. 9. — Pilobolus roridus. Dia- 

 grammatic representation of 

 octohedral crystalloids in 

 the stipe of a fruit-body : a, 

 the cell -wall ; b, the parietal 

 protoplasm ; cc, the cell-sap 

 of the great vacuole ; d, a 

 crystalloid in the cytoplasm ; 

 e e, crystalloids in the cell- 

 sap ; /, a crystalloid which 

 is hollow in the centre. Some 

 of the crystalloids have con- 

 cave faces. Magnification not 

 stated. Copied by the author 

 from P. van Tieghem's 

 Nouvelles recherches sur les 

 Mucorinees {Ann. Sci. Nat., 

 T. I, 1875, Plate I) and re- 

 produced on a larger scale. 



