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. 11 1) : 
Die Verschmelzung zwischen cler 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 unmittclbaren 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, Euchaiis, 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. 
