472 AMERICAN JOURNAL OF BOTANY [Vol. 8, 



that the pollen tubes of Agrostemma Githago bore through the membrane 

 of the stigma papillae as evidence for a cytase in pollen. Czapek also refers 

 to the investigations of Rittinghaus (1886, pp. 105-122) as confirming the 

 opinion of Strasburger. The observations of Rittinghaus may, however, 

 be interpreted quite differently, and point quite as definitely to the presence 

 of a pectinase, as of a cytase. Rittinghaus examined numerous flowers, 

 including Ipomoea, Convolvulus, Alisma, Agrostemma, Lychnis, Phlox, and 

 Silene. He writes (p. in): 



Die Verschmelzung zwischen der Cuticula der Papille und der Cellulosemembran des 

 Schlauches ist ganz deutlich zu erkennen, und es leuchtet ein, dass die Liicke in der Cuticula 

 ihre Entstehung nur einer unmittelbaren Einwirkung der Pollenschlauchspitze verdankt. 

 Das losende Agens ist somit nur im Plasma des Pollenschlauches zu suchen. Uber die 

 Natur desselben ist einstweilen leider nichts zu eruiren, zumal das einzige uns bekannte 

 Cuticula-losende Reagens kochende Kalilauge ist. Vielleicht wird man spater die Erschein- 

 ung durch die Gegenwart eines besonderen Enzymes aufklaren konnen. 



J. R. Green (1891) noted amylase in pollen tubes. Green's later re- 

 searches in 1894 are by far the most careful and complete experiments on 

 pollen enzymes which have so far been reported. They will be briefly 

 reviewed on a later page. Strasburger (1886) mentions diastase and invertin 

 as present in pollen grains prior to germination. Sandsten (1909) reports 

 invertase and diastase. Later, Kammann (1904) found protease, diastase, 

 catalase, and lipase in rye pollen but does not give details of his experiments. 



In the investigations of Green (1894, pp. 385-409) the pollen was pow- 

 dered with glass and the powder suspended either in glycerine, or in a 5 

 percent solution of NaCl, to which 2 percent of potassium cyanide was 

 added as an antiseptic. In other cases chloroform (a few drops) or oil of 

 cinnamon was used as an antiseptic. The 5 percent NaCl solution proved 

 preferable to glycerine. Diastase was found in the pollen of Gladiolus, 

 Anemone, Antirrhinum, Tropaeolum, Pelargonium, Crocus, Brownea, Hel- 

 leborus, Alnus, Tulipa, and Clivia; also in that of Zamia after germination 

 begins. Experiments failed to show any sufficient evidence for diastase 

 in the resting pollen giain of Zamia, and starch makes its appearance in 

 these pollen grains only on germination. Diastase was absent from the 

 pollen of Lupinus, Lathyrus, Eucharis, Richardia, and Narcissus. The 

 diastase, according to Green, dissolves the starch without corroding the 

 grains. The pollens tested for invertase were those of Eucharis grandiflora, 

 Narcissus papyraceus albus, N. Pseudo- Narcissus, Helleborus, Richardia, 

 Lilium pardalinum, and Zamia Skinneri. It was found in these, but was 

 absent from the pollen of Alnus and of Clivia. He reports that 



A few experiments were made with a view to determining the existence of a cytolyst 

 and a proteolyst, but in no case could either be found. 



In the case of Eucharis grandiflora, tested for invertase, Green says that 



Only the contents of three or four anthers were used, yet a workable quantity of 

 invertase was extracted. 



