88 BOTANICAL GAZETTE [JULY 
on A. campestris, and less abundantly on A. platanoides, but not at all on 
A. pseudoplatanus.. R. pseudoplatani infects only A. pseudoplatanus, upon which 
it occurs in company with R. acerinum platanoides. 
Infection by the spores of Rhytisma always takes place on the lower sur- 
faces of the leaves. Observations during a period of six years show that there 
is a parallelism between the severity of the disease and the quantity of rainfall. 
No appreciable injury results to the trees from the attack of the fungus. 
~ An experiment carried out by Leste and reported by TuBEUF* confirms 
in part the results of Mutter. Leaves of Acer pseudoplatanus, bearing 
sclerotia with ripe ascospores of Riytisma, were suspended over pot-plants of 
A. pseudoplatanus, A. platanoides, A. campestris, and A. Negundo. Of these 
only A. pseudoplatanus was infected, showing that the fungus was unmixed 
R. pseudoplatani of Mitter—H. HassE.princ. 
between the cytoplasm of the egg apparatus and the cytoplasm of the middle 
portion of the sac_—CHarirs J. CHAMBERLAIN 
Nuclei in sieve tubes.—It is generally accepted that the nuclei of sieve 
tubes soon disorganize and disappear, even such investigators as STRASBURGER 
(891) and ZACHARIAS (1895) having failed to find nuclei in the mature tubes. 
By using the careful methods of modern cytology, Scummp1* finds that in 
Cucurbita Pepo, Victoria regia, and Trapa natans, the nuclei can always be 
demonstrated, even in the older sieve tubes. The technique of 1891 and 1895 
Was sufficient for the demonstration of these nuclei, but apparently it was not 
thought worth while to use such tedious methods in anatomical work. SCHMIDT 
Promises a paper on the structure and function of the sieve tube. —CHARLES J- 
CHAMBERLAIN. 

*Tuseur, K. von Rassenbildu : ; . + ochr. 
: , ng bei Ahorn-Riyt; 5 turwiss. Zeitsc 
Forst- u. Landwirtschr. IIi21-24. 3 . es ae geese 
* BLACKMAN, V H.,and Wet 
‘: »V-H., SFORD, E. J. ization in Lilium. ‘Ann. Botany 
27:111-114. pl, 12. dors, J., Fertilization in Lilium 
* Scumipr, E, W 
1913 »&- W. Der Kern der Siebréhre. Ber. Deutsch. Bot. Gesells. 31278, 79: 

