460 



BOTANY 



PART II 



and on Euphorbia, is simpler than the other Uredineae and forms neither 

 uredospores nor teleutospores. The mycelium proceeding from the basidiospore 

 consists of uninucleate cells and forms spermogonia and aecidia. The binucleate 

 condition is attained as in Phragmidium by cell-fusions of the cells that will then 

 give rise to the chains of aecidiospores. The mature aecidiospores behave like the 

 teleutospores of the other Uredineae ; their two nuclei fuse, and the spore germinates 

 to form a basidium bearing four uninucleate basidiospores. This is preceded by 

 a reduction division of the nucleus (Fig. 408). Possibly Endophyllum may be 

 regarded as a primitive form. Caeoma nitens behaves in the same manner ( 81a ). 



Order 3. Auricularieae 



The basidia, as in the case of the Uredineae, are transversely septate, with 

 four spores. Only a few forms are included in this order. Among the most 



7" 



x 



Fio. 408. Endophyllum Sempervivi. 

 A, Young aecidiospore, still bi 

 nucleate. B, Mature uninucleate 

 spore. C, Germinating spore the Fio. 

 nucleus of which has divided to 

 form two. D, Aecidiospore which 

 has germinated to form a young 

 four-celled basidium. (After HOFF- 

 MANN.) 



409. _ .Exobasidium Vaccinii. Transverse section 

 through the periphery of a stem of Vacdnium. ep, 

 Epidermis ; p, cortical parenchyma ; m, mycelial hyphae ; 

 b', protruding basidia without sterigmata ; b", with 

 rudimentary sterigmata ; b'", with four spores. ( x 620. 

 After WORONIN.) 



familiar is Auricularia sambucina (Judas's ear), found on old Elder stems. 

 It has gelatinous, dark brown fructificatio'ns, which are shell-shaped arid bear 

 on their inner sides the basidial hymenium. 



Order 4. Tremellineae 



The basidia are longitudinally divided (Fig. 398). The hymenium is situated 

 on the upper surface of the fructifications, which are generally gelatinous and 

 irregularly lobed or folded. The few genera included in this order are saprophytic 

 on decaying wood and tree-trunks, on the surface of which the fructifications are 

 produced. 



