38 BASIDIOSPOEES 



air, moreover, i he four cells may qoI be formed ; the " basidium 

 may rcsoinblc, more or less, an ordinary germ-tube and possibly 

 may function as such. Even if the torn- cells are formed, bhey 

 may germinate by the protrusion of a germ-tube, which pre- 

 sumably can cause infection by penetrating the cuticle (see 

 Coons, 1912. ]». 225). But, with access of air, each cell forms a 

 sterigma and a basidiospore as previously described. The-. 

 conidia are obviously adapted for wind-dispersion. If they 

 alight on a suitable surface, they send forth a short tube which 

 invariably bores straight through the cuticle into the under- 

 lying epidermal cell of the plant, and there begins to form 

 a mycelium. The only instance in Puccinia known to the con- 

 trary 1 , out of the many observations that have been made and 

 figured of this process, is De Bary's record of the case {Ann. 

 Sri. Nat. Bot. 4. xx, 1863, pp. 88-9) where the germ-tubes of the 



basidiospores of Puccinia Dianthi 

 (q.v.) penetrated through the stom- 

 atal openings of Diantlius barbatua 

 (Fig. 24). In grasses and sedges, it 

 is easy to see that the siliceous 



cuticle would present a great ob- 

 Pig. 24. Basidiospores lb) of . , „ , , 



Puccinia Dianthi, germina- stacle to the entry ol such a tube, 



ting on leaf of Dianthus, wn il e not impeding germ-tubes 

 showing the germ-tubes mak- , r ° ° 



ing straight for the stomata which enter through a stoma, and 



(afterDeBary'Bfignre). x390. ^ ig probably the reason why 



secidia are so rare on the order Glumiflorse. In the hetercecious 

 species no one has yet brought forward indisputable evidence 

 to show that basidiospores can infect the host which bore the 

 teleutospores, although statements to that effect are made. 



The shapes of basidiospores are not irregular ; they are 

 more or less constant in each group. In Puccinia and Uromyces 

 they are ovate, somewhat flattened on one side, or kidney- 

 shaped. In the Phragmidiea? they are almost spherical ; in 

 the Melampsoraceae small and roundish. In Endophyllum they 

 are ovate; in Goleosporium they are large and ovate and a 



1 Statements have been made of other instances, but most of them on 

 insufficient authority, and some have been specifically disproved. The genus 

 Coleosporium seems, however, to be an exception. 



