1907] CURRENT LITERATURE 



71 



place. Such megaspores form prothallia whose nuclei have 2x chromosomes 

 and finally an egg is formed with 2X chromosomes, and this egg develops an 

 embryo with 2X chromosomes; so that the sporophyte number of chromosomes 

 is maintained throughout the hfe-history. But in the same species there are 

 instances of reduction of chromosomes, so that prothallia and egg have the x 

 or gametophyte number. 



In forms which produce apogamous embryos, microsporogenesis is likely 

 to be abnormal, the development often stopping before the nucleus of the micro- 

 spore mother cell divides; but here again normal microspores with the reduced 

 number of chromosomes are sometimes formed. The nuclei of the x and 2X 

 prothallia can be distinguished in a general way by their size, the diameter of the 

 nuclei in 2x prothallia being about one -third greater than those in x prothallia; 

 also the diameter of the eggs with 2X chromosomes is about one-fourth greater 

 than that of eggs with the reduced number. 



Strasburger uses the term apogamy rather than parthenogenesis because 



he regards an egg with 2X chromosomes as a purely vegetative cell. He would 



* use the term parthenogenesis only in case an egg with x chromosomes should 



I develop an embyro without fertilization. Even if 2X chromosomes should appear 



at the first mitosis in such an egg, he would still regard it as a genuine case of 



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parthenogenesis. 



The preparations naturally showed many stages in the development of spore 

 membranes. Shortly before the spore reaches the periphery of the vesicle con- 

 taining it, the perinium appears. This is a deUcate, fine-pored membrane 

 {Hautchen) laid down upon the surface of the vesicle by the surrounding tapetal 

 Plasmodium. The prismatic layer is then laid down upon the delicate membrane. 

 The exine, mesopore, and endospore are then developed in succession upon the 

 protoplast of the spore. This study supports the view that cell membranes 

 arise only in direct relation with protoplasm. — Charles J. Chamberlain. 



Items of taxonomic interest.— S. M. Bain and S. H. EssARY (Jour. Mycol. 



12:192, 193. 1906) have described a new anthracnose of alfalfa and red clover 



i (Colletotrichum trijoUi), which is said to be the most serious plant disease occurring 



in Tennessee.— J. M. Greenman (Field Columbian Mus. Publ. Bot. Ser. 2:185- 

 igo, 1907) has published 10 new species of Citharexylum as preliminary to a 

 synoptical revision of the genus.— E. Hassler (Bull. Herb. Boiss. II. 7:161-164. 

 fii^- 5- 1907) has described a new genus (Dolichopsis) of Leguminosae from 

 Paraguay.— L. A. Dode (idem 247, 248. figs, 3) has described a new species of 

 Juglans (/. elaeopyren) from the Santa Catalina Mountains of Arizona; it is 

 distributed in Pringle of 1881 as /, rupestris Engelm., and the type is in Herb. 

 Barbey-Boissier.— A. H. Moore (Proc. Amer. Acad. 42:521-569. 1907), in a 

 revision of the confused genus Spilanthes, recognizes 63 species; describes as 

 new 2 subsections, 8 species, 4 varieties, and 7 forms; and makes 14 new com- 

 binations.— W. H. Blanchard (Torreya 7'5S-57- ^9^l) ^^^ described a new 

 Rubus (blackberry) from the vicinity of Philadelphia and Washington.— J. R. 





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